Thought I'd throw a bit of my recent experience into the mix here as I've been thinking about a change and did a few 'tests' on new years day. Back to back comparison with a couple of mates and a bit of a car swap, we did: My Z4MC, E92 M3 (which I've driven a fair bit before), 997 Carrera 2 (early model)...
First and foremost, all really nice cars, but I came away thinking that the Z4 is still the most 'special' in terms of 'pure sports' experience.
- The M3 is undoubtably the fastest and really comes alive when you get into the higher revs / start piling on the speed. Day to day (or with no experience) I would certainly say you can drive this faster than the Z4M.
- Porsche was really nice in terms of build quality etc, but (for me) the engine didn't feel anywhere as exciting as that on either of the M cars. I'm also not convinced it's a quick at the Z4M either, although I'm sure you'd learn to drive it and get more in tune / quicker over time (which in itself is appealing for me).
- Both of my mates commented on how aggressive the Z4M felt, although that could be partly down to my suspension set up.
Biggest reason for wanting to do this was that I've been hankering for a Porsche, but I think I'll need to step up to a more 'specialist' model (GT3?) to gain anywhere near the excitement of the Z4M. After driving them all back to back, I'll keep the Z4M for now, but I'd be tempted by an E90 M3 Saloon when I need space for baby seats!
Other than that (and as a few people have already said from reading this tread), I really think we're going to struggle to get anything as special / exciting / fast / fun as a Z4M without doubling the budget (at least!)... Oh yeah, and fuel economy wise... the S54 is brilliant considering how much power you're getting!
We saw an i8 cruising about on the day too, but he didn't seem to want to 'play'. Have to say it looked pretty cool on the road and I'm of the opinion that it's an interesting car that suggests where the future direction of 'electric / hybrid' could go, and for that reason I'm pleased to see them out there... I definitely wouldn't mind a blast!