To be honest, it's not a big secret. We decided to come clean and announce our intention to bring a competitor car along, and the response from Renault was commendably relaxed. Mind you, there's every reason for Renault to feel confident. The Megane is the latest product from its Sport division, which is on a bit of a roll at the moment; in the last six months it has given us two absolute corkers in the Clio 182 and the second-generation Clio V6 255. If I were a betting man, I'd have a few quid on the car with the big bum.

Exactly which car to bring along as the benchmark was the subject of some debate. With a turbocharged 222bhp fed through its front wheels and a price of ΂£19,500, the M΃©gane could be compared with the cheaper 200bhp Cooper S Works or Civic Type-R, or the more expensive Alfa 147 GTA. Come to think of it, the four-wheel-drive Audi A3 3.2 or Subaru Impreza WRX could easily be on the shopping list, too. Heck, if we could clone a small army of Haymans we could have brought them all along, and the recently discontinued Golf R32 and Focus RS too.

In the end we settled for none of the above. Instead, Hayman has made the trip in the SEAT Leon Cupra R, which has an identical, turbo-assisted power output, front-wheel drive and carries an ΂£18K price tag. It's as close to the M΃©gane in concept, size and price as anything out there. It also happens to be one of our favourite hatches. And here at the prescribed location are Mr Hayman and the Leon, basking in the warm sunshine, overlooking a spectacular vista. It's not all bad being a road test assistant.

Visually, there's nothing quite like the Megane, except perhaps the larger, now discontinued Renault Avantime. From the rear three-quarters in particular, the three-door Megane looks like a scaled-down version of the luxury four-seater. To my eye, the enhancements that mark this out as the Renault Sport Megane - the signature twin central tailpipes, the subtle tailgate spoiler, 18in wheels and a pair of front driving lamps outboard of the wide-mouthed grille that look like they should be sprouting short tusks or mandibles - fail to turn it into an obviously sporty car. It's not the additions, it's simply that the basic shape isn't very dynamic. Not that this has been a hindrance to sales across Europe - the extensive and multiple-bodied Megane range now accounts for 40 per cent of all Renault sales.

As you'd expect, an appropriate amount of effort has been expended on the hottest Megane's chassis. Putting more than 200 turbo'd bhp through a pair of wheels that also have to steer can be a rather fraught exercise, as the rampant Focus RS has shown. It's a problem that Renault Sport' has worked hard to crack. Unlike other models in the Megane range, the 225 has a clever version of the MacPherson strut front suspension. The steering axis in the conventional set-up is determined by the upper and lower mounts of the strut but the 225 has a hollow, cast aluminium upright bolted to the lower end of the strut that locates the hub carrier and almost halves the off-set of the steer axis. This is said to reduce the sensitivity of the wheels to the loads applied under hard acceleration and braking.

It certainly seems to work. Heading up the mountain to meet with the SEAT, the M΃©gane's front wheels rarely wriggled as full power was applied, even scurrying away from hairpins. Yet the power delivery also seemed to be playing a part. The Megane feels seriously potent on boost, yet the delivery is remarkably linear, with no unsettling spike of torque for the front wheels to wrestle with. The ride, too, is a factor; the suspension seemingly ironing-out the surface's worst ripples and pocks.

Nose to nose, the Leon appears to be bigger than the Megane but is actually 45mm shorter overall. It's a clever illusion that the Renault's lines play, and the five-door version of the 225 is the same length, just 20kg heavier, and costs ΂£500 more - or exactly ΂£2000 more than the five-door-only SEAT. Essentially, the Spaniard's chassis is the same with struts up front, a torsion beam at the rear, Brembo brakes, stability control and identically-sized 225/40 ZR18 tyres. In detail, the Leon lacks the clever lower strut but boasts ventilated discs all round (the Megane has plain rear discs) and wears Pirelli P-Zeros as opposed to Continental SportContact 2s. It weighs in at 1376kg, 20kg more than three-door Megane, so we pretty much have parity.

Stepping from the Megane into the dark cabin of the feistiest Leon is a bit of a shock, though. This particular Megane carries its metallic burnt orange exterior through to the interior, its mid-grey trim shot subtly through with the same hue. It lends a certain cohesion; the orange seat belts, the seam stitching and the hint of orange backing to the perforated leather.

Choose not to tick that option box (and save ΂£600) and the highlights of the interior are glossy 'piano' black, applied to the bezels of the dials, the gear lever surround and the arms of the awkward aircraft-style handbrake. Whichever trim option, the Megane has a chunky, grown-up feel with deeply sculpted, sporty seats, and multiple adjustments to tailor a good driving position.

The SEAT feels like a dark hole in comparison. You sit lower, the plastics and fabrics appear less expensive, and even the roof lining is black. Dark red stitching, 'R' logos and white-faced, silver-edged dials lend little relief. Get going, though, and you appreciate that the seats are equally supportive and that the steering wheel, with its questionable, rally-style red leather band marking the centre point, is better to hold.

More than that, the Cupra R's wheel gives access to a chassis that feels initially less settled and poised than the Megane's but which on extended exposure seems appealingly raw and honest. The SEAT's engine has more character too; a more gravelly, urgent note - and that's something I never thought I'd write about the Volkswagen Group's normally anodyne 20-valve turbo. It delivers the same horsepower but, being a 1.8 rather than a 2-litre, lacks a little of the Megane's torque, and it also delivers its peak power slightly higher up the rev-range. Perhaps as a consequence, it's a bit fizzier, a bit more exciting in its delivery. That said, this is all relative; a Focus RS would feel like a car possessed by demons.

Some of the roads here are every bit as tough as you'll find in the Black Mountain region we know rather better, the one in Wales. They're a stern test of a 222bhp front-driver and there's a ticklish compromise to be struck between sparing you from the worst the surface throws up and feeling connected to what's going on at the front wheels.

The Megane rides better, quietly dealing with the worst the road can offer, and its steering is less prone to distraction, but it does leave you feeling isolated from the action. It's not the fault of the ESP traction control system, which is always engaged above 30mph, even if you switch it off, because it's set to intervene 'late and hard'. It allows some slip and slide and it's impressive how much of the Megane's performance you have to use before traction and grip are exceeded.

No, it's something more than that, and it was only after a good strop in the Leon that it became clear what it was. The SEAT feels a fraction stiffer, its wheels seem to have less travel and its ESP warning light flickers more frequently. It's subtle in actuation, though (soft and early, Renault might say) and if you switch it off you're not unleashing some monster. Even going hard, the tail remains glued, giving it a nose-led feel with strong lateral grip, a flat cornering stance and fine feel through the rim of the steering wheel.

You can edge up on the Cupra R's front-end limit and use the spikier delivery of its engine to edge out on to a widening line exiting corners. Sure, bumps can set off a bit more wheelspin, but there's enough feel for you to be able to modulate the throttle and have the satisfaction of being your own ESP system. It's fun in a straight-forward, almost old-fashioned fast hatch sort of way. The six-speed shift isn't the slickest but no worse than the Renault's; the power of the brakes is impressive, the brake pedal itself can feel wobbly as if there's some play in its bearings, but the Leon is fundamentally a well-sorted, quick, exciting and exploitable hatch.

Over the same roads the Megane rarely puts a wheel wrong but it's not an involving or especially engaging experience. Crucially what it lacks is decent steering. It has electric power assistance with 12 settings, weighting up as speed increases, but feel through the wheel is lacking. You don't feel connected with what's going on at the front wheels, whether you're hacking down a bumpy road or, as we were later, flowing along a gloriously smooth, wide and gently flowing main road. The Megane didn't adopt the easy gait of a responsive fast hatch; it felt reluctant to deviate from the straight-ahead and the weighting on lock was a fraction too much, seemingly masking any feedback that might be there.

That lack of stimulation extends to the performance. The Megane is unquestionably a quick car, but the engine's delivery is strangely flat. Even the very capable, quiet ride seems to isolate you from the action. It seems slightly perverse to say it, but the fastest Megane is almost too good to be the serious, super-fast hatch the specification (and Renault Sport's reputation) would lead you to expect.

Anyone who needs to up-size from the brilliant Clio 182 might think that the Megane 225 was the obvious choice, but if it's the same thrills you're after, sadly it isn't. And it's a good job I'm not a betting man, because the Leon Cupra R, although less than flawless, is the better driver's car by some margin, and more affordable, too.