Why the comparison?
Well, summer is supposed to be on its way and what could be more sunshine-friendly than a couple of sleek open sports cars? This pair of brawny roadsters is vying for the same buyer, with the BMW using its badge and breeding against the Nissan's sharp looks and a heritage dating back to the original Z-car of the 1960s. So, both have pedigree, performance and poise, but which one will be driving off into the sunset?
How are they similar?
Foldable roofs, two seats and muscular six-cylinder engines mark out the BMW and Nissan. They may not be the most environmentally appeasing cars, but to the dedicated enthusiasts who love serious performance to tousle their hair, few can match these two. Each has distinctive looks and both nip off 0-62mph in less than six seconds. The BMW is the swifter, taking 5.2 seconds to the Nissan's 5.5 seconds, but neither is what you'd call slovenly. They both share an electronically limited top speed of 155mph and, for the purposes of this test, each has a six-speed manual gearbox. The BMW can be specified with a double-clutch, six-speed automatic gearbox where the Nissan has the option of a more conventional seven-speed automatic transmission.
If they cannot be separated on paper performance, it's much the same on the road for straight-line oomph. The engines in both love to be revved hard and sound terrific when pushed to their limits. Even though the BMW uses twin-turbochargers, there's no lag or delay in its power delivery, so it matches the 370Z every step of the way. With their roofs lowered, this pair is brilliant at delivering a smile to your face and you to where you want to be. Put the roofs up and they transform into reasonably hushed GT cars with small but usable boots. For everyday use, the Nissan and BMW share the same basic luxuries, such as electrically operated roofs, air conditioning, fine CD stereos, alloy wheels and leather upholstery.
How do they differ?
The Z4 and 370Z may share the basics of a svelte roadster, but the Nissan is way out in front on the equipment count, and it costs substantially less than the BMW. To bring the Z4 up to the same specification as the 370Z, you'll need to add cruise control, heated seats, power folding mirrors and Bluetooth connection. This all adds up to £1,215 of extra kit for the BMW that is already part of a 370Z Roadster GT, which makes the Nissan more than £6,000 cheaper than a similarly equipped BMW. The only points where the BMW outscores the Nissan here is the German has an Isofix child seat mount and a passenger airbag that can be switched off to accommodate a child seat.
However, the Z4 sDrive35i begins to win back considerable ground when it comes to running costs. The BMW emits 219g/km of carbon dioxide, so avoids falling into the heaviest pollution banding for road tax and company car tax, while the 370Z's 262g/km put it firmly in the top bracket for both. Added to this, the Z4 turns in a reasonable 30.1mpg combined economy to the Nissan's 25.2mpg average. The BMW also scores a lower insurance ranking, coming in at group 43 to the Nissan's group 47, and the predicted servicing costs for the Z4 work out at about two-thirds of those for the 370Z.
Facts and figures aside, this pair also show some more fundamental differences on the road. Where the BMW has a supple, cosseting ride, with the option of firming it up for sportier moments courtesy of the Adaptive Chassis Control, the Nissan simply feels too firmly sprung much of the time. The 370Z still has plenty of grip and steering with good feel for confident cornering, but it just cannot quite get on terms with the fluency of the BMW's suspension, nor with its composure and comfort. However, the engines in both cars are huge fun to use and the Nissan even comes with a system that blips the throttle on downshifts for the perfect change every time.
So which one would we have?
This is a very tough decision. On the one hand, there is the value for money of the Nissan 370Z in GT trim that comes with so much standard kit at a keen price. It also looks great, goes well and its fabric convertible roof is quick and simple to use. Balanced against that is the BMW Z4 sDrive35i's lower running costs, better ride and handling balance and a folding metal roof that gives more security when it's raised. All said and done, it's the slimmest of wins to the BMW because we're judging sports cars here and we can forgive its higher price for the extra thrills it delivers over its Nissan rival.