Parkers overall rating: 4.4 out of 5 4.4

The Z4 is more of a refined, cruising convertible than outright sports car – mainly because you can’t help but compare it with the excellent Porsche 718 Boxster. However, as an open-topped sports car that you can use every day, it’s very impressive indeed, especially in entry-level sDrive20i spec.

It manages to be a great long-distance cruiser that’s relaxed and comfortable, but is also capable of turning into an engaging roadster that can genuinely put a smile on your face on a twisty road. Throw in the luxurious, high-tech interior and lengthy standard kit list and it’s well worth a look.

That leaves the rest of the range as a bit of a question mark. At the other end of the scale, the M40i may appeal to the enthusiast due to its silky smooth and powerful 3.0-litre engine and M badge, but in most situations you may well have more fun in the lower-powered cars. The M40i and its exotic soundtrack almost feels like a muscle car in nature -  with its torquey engine you cover journeys in a more relaxed manner – plus, with that feeling of being a little heavier and slightly less adept at handling a country road, you back off the pace anyway.

Arguably, the 30i is the best all-rounder that ticks all the boxes, being more powerful than the 20i and retaining a higher level of agility over the M40i. However, the 30i still retains a rather soulless engine and doesn’t necessarily add a huge amount of extra excitement or shove, so for those sun-seekers purely looking for a Z4, you may as well just opt for the 20i.

That means you get all the best bits of the range at lower cost, and may even have some extra cash spare for a couple of optional extras. We’d consider the Comfort Plus Pack for the useful everyday features such as electric seats, keyless entry and wind deflector, while the Technology Pack bolsters the already-generous kit list with an upgraded stereo, head-up display and automatic parking.

If you want a more engaging sports car, the Porsche 718 Boxster will be for you, while the Audi TT Roadster offers similar practicality levels but with a simpler, more modern vibe inside and out. However, the Audi doesn’t quite feel as impressive a long-distance cruiser as the BMW and can suffer from more turbulence in the cabin with the roof down.