Really a matter of personal taste and I feel that it also depends upon the color of the car as well...
After a few years of debate I went with these...
Isn't that a white Z4M in the pics above ? And if so I'd bet they are genuine CSL's...
I went with CSL reps on mine although I am toying with a set of BBS CH's as I am now planning on keeping the car a little longet than planned when I bougth the reps.
This is a complete opinion thing. I hate some of the rims I see...particularly some of the aftermarket ones that are the most sought after...so I won't mention any names I just know I don't like 16 in rims on a non sport model. But I love my stock 17 inchers (106 style) on my sport model. The sport option with it's lower rise height makes a HUGE difference IMHO. BUT as long as you like them...who cares!!!
...although this is a great thread to for people to post pics and do side by side comparisons for future shopping!
I'd take that bet - remember, real CSLs are very rare in the US and (as my aching wallet can attest) very expensive to bring here. They don't seem as desirable in the UK (where they're readily available). The only white Z4MC on the forum with them that I know of is UK member sixspeed's and his were re-finished to gunmetal.
As for my opinion, on the roadster my favorites are, in order, the 108s (2-piece 5-spokes known for corrosion), 107s (ellipsoids), and 104s (turbines, if I've got the number wrong). I also like the ZHP-style wheels on them as well.
I personally like the stock turbine ones (not sure the real name but they look like a fan rotor) followed by the er ellipsoids (the ones I have on mine and IMZ4N got chromed on his)
I personally think the 108s look best on the roadster. I was tempted to get a set but was put off by the apparent problems with bubbling and corrosion. I went for MV2s which are my all time favourite alloys, and which I also think look good on the z4.