The S2000 is one of those cars that we really ought to like a lot more than we do. It's a no-nonsense, rear-drive sports car with a 237bhp, 9000rpm in-line 'four' and a close-ratio six-speed gearbox that, if you were compiling a list of the best gearshifts in production, would be very close to the top. As a package, though, the Honda has left us oddly unmoved; the 1999 original attracted flak for its engine's lack of low- and mid-range vigour, and its chassis' lack of focus. The latter was notably improved for 2002 but for us the S2000 remained better on paper than it was in action.

This year's model ushers in another round of chassis changes and the first cosmetic overhaul. The new, ten-spoke, 17in alloys (up an inch in diameter) with their slightly wider and lower rubber are crucial to both, being the obvious visual identifier and the starting point for the many detail chassis mods.

The revisions are timely. The shock of Chris Bangle's 'flame surfacing' lines on the Z4 has cooled, leaving a roadster that smoulders with showroom appeal. At the S2000's ΂£27K price-point, the Z4 2.5 gives you a 192bhp straight-six that's creamy and musical and an electric hood that folds away in ten seconds.

All credit to Honda's stylists, though; the low-nosed, wedge-shaped S2000 looks better than ever. At the front there's a bigger, squarer, more aggressive air intake; at the rear the bumper apron flows around and incorporates the bigger oval tailpipes, and both front and rear have details that echo the swage line on the lower body between the wheels. It looks much more cohesive, even in our test car's garish pearlescent yellow paintwork.

Considering the similarity of their front-engined/rear-drive layouts, the S2000 and Z4 are poles apart on the road. The BMW initially feels like the softer, more easy-going roadster you'd expect, its torquey straight-six punting it around effortlessly, its suspension feeling compliant and cosseting. The S2000 feels more hard-edged, its ride seemingly firmer and less absorbent, its in-line four growling coarsely.

Honda doesn't claim any changes to the 2-litre VTEC 'four' but we can't believe it's in the same tune as the original S2000. The spec sheet says it still produces an incredible 237bhp at 8300rpm and a weedy 153lb ft of torque at 7500rpm, while the gearing is exactly as it was, thanks to lower profile rubber on the bigger rims. So nothing has changed, apparently, yet the S2000 now delivers adequate urge in a high gear from low revs, and more than adequate oomph at moderate revs. And the fact that it does changes everything - the S2000 is no longer a car that only starts to make sense when you're on the right road, in the right gear, at over 6000rpm.

That's bad news for the Z4, especially as after a few miles you realise that those sexy 911-esque 18in split-rim alloys (an option that's hard to resist) are a mixed blessing. The apparently supple demeanour of the Z4 is thrown into turmoil by a less than smooth road, which is to say most UK roads. It's not all down to the wheels and tyres, but experience of the new Z4 2.2i, which comes with the same 16in rims and tyres that are standard on the 2.5i, suggests that the upgrade doesn't help.

While the firm ride of the S2000 is entirely honest, picking out small bumps at low speed but, as the pace quickens, delivering good control and progression, over the same road the BMW goes to pieces; its steering distracted by cambers, its ride suddenly choppy like the run-flat tyres are full of concrete. Add in electric power steering whose weighting shifts artificially and you're left with a rather jumbled picture.
In contrast, the S2000 is now much more exploitable, particularly because its tail-end is now more progressive in its reactions. Changes include a lower rear roll centre, slimmer anti-roll bar and less geometry shift under load, and also a slower steering ratio that raises the turns between locks from 2.25 to 2.63. In league with the new tyres, the result is greater composure that allows you to feel and work the front and rear more confidently. The engine's stronger delivery at sub-VTEC levels helps, too.

With its angry-sounding in-line four, the S2000 is no loping cruiser. The torquier Z4 does that better, yet with its agitated ride it's not as comfortable as it could be, which means it's neither a good cruiser nor a honed driver's car. The Honda has a greater sense of purpose. Interior revisions have liberated a little more elbow room but the cockpit still feels a tad tight and the fixed wheel a fraction low, but it's a pure driving tool with a keen chassis, manic engine and fabulously slick gearshift.

Five years after launch, the S2000 is the car we hoped it would be. BMW has some catching up to do.