As someone who owns a Z4, and thus visits the Z4 forums which are dominated by Z4 M owners, let me tell you no. Most of the times it's around $900-1200 from what I've seen. You can actually do the valve adjustments yourself (or a friend); it's just you lack the tools (which cost less than $500 total). Most of the DIYers say it took them 6-8 hours. It's very important work that takes a while, but that doesn't make it difficult.

 

M3 no question. That's based on my driving experience with a 350Z though, plus, I'm not sure if this is in addition to our existing cars[?] The 4-seater no doubt in our current scenario.

"Same miles" kind of implies used, so is the M3 CPO'ed (or equivalent)? BMW maintenance can be a touch high (based on us owning a Z3, 328Ci and X5 4.4i).

 

I test drove a 370z. Beautiful car. I had fun driving it. I never drove an m3 but the maintence cost is enough to show me away. I always wanted to drive one though.

 

 

M3 every single time.

More practical. Engine is light years ahead of any Z (I drove the nismo 350 and the 370), silky smooth and a joy to rev up. Superb handling and stability at speed. Suspension is a tad stiff but not unmanageable. The car is a complete package, and clean examples are getting hard to find. I miss my PY car every day.

Definitely invest in a good aftermarket comprehensive warranty, these cars are maintenance intensive. But the difference in driving joy is well worth it.

No brainer IMO

 

370 because my pockets are anti German.

 

M3 but I would prefer a Z4M.

I just love the S54 engine.

 

Ive driven both.
The 370z is a nice ride, I dont know what everyone is getting on it for about the shifter, I found it to be short enough, good engagement feel, a tad rubbery, but overall I was impressed by it. Not as good as an s, but if I owned an M3 I wouldnt be snobbing it. The M3 throws are a tad longer, but are smoother and feels like like light switches in the way they engage, but can also be rubbery as well.
Steering feel, I'd say tied, there are subtle nuances of both and I'm sure the BMW purists will say the bmw is better, imo I just prefer the steering wheel of the m3 to the Z.
Engines. I love both, I dont know what people were saying about the vq motors not being smooth, they're about smooth as they come. The S54 is pretty much an f22c with two more cylinders, manic power, but smoother. But I dont like how the vq drops off at the end, so I'd say the M3 is better for spirited driving, the Z is better otherwise.
Handling, I didnt spend enough time with either to really give a good comparison between the two, but in the right hands either could make the other look foolish, so toss up.
Ownership costs, I'm not sold on the 370z being typical japanese low maitenance and being highly reliably. So with that said, owning either at this point out of warranty will make me a little worried. That said, I know the M3 is going to cost me some decent money. You guys mentioned valve adjustments. In an S at the dealer, I could get it done for 200 bucks, the M? Try 500+. Annually (not in the book, but highly recommended). 30K maitenance really is more an inspection and lubing, but the major ones like the 60 or 100 will cost you dearly, and it seems like theres always somethign that needs to be done.
Also, main difference between the two is that any reputable mechanic can work on a nissan car after enough years go by, I'd still be skeptical to let anyone but a bmw specific mechanic touch my M, so in that lies more costs.

So with all that said, I love both, but I'd lean on the M3 only because I know more about that car since more time has elapsed. That said, I've been spending my time researching 07-08 350zs...

 

Pretty typical discussion so far.

BMW makes the superior car. Yet most people will go Asian due to maintenance costs.

 

If you prefer garbage buy the Z. But if you don't like sitting inside a dumpster look else where.

This is the best advice I could provide.