Having owned both... 4 years in the Mcoupe and 2 years with the Mroadster... The roadster is the better experience from feeling in touch with the road, noise and feel, the coupe can't really come close too and I was always a little disappointed with the noise in the coupe.
In the roadster you get equal exhaust and induction and the wind in the hair element goes a long with in the driving experience imo. I was generally surprised how much better it is in the Roadster coming into buying one thinking I knew a lot about the cars dynamics and I was wrong.
In the coupe your far more cocooned, its more droney on the motorway (I actually really struggled to get used to it for the first 3-4 months with headaches etc def something to get used to) but you get quite a bit of induction noise. In fact I didn't realise it sounded so good until I was photographing panning shots of the Z4MC.
The coupe really is gorgeous, marginally better to drive because of its faster rack and has the stiffer chassis but not 100% sure that's beneficial on an already very stiff car. It also gets more attention and is a special car. The Z4Mc I had was in a few magazines and I photographed it a lot so there was an element of additional attention in car circles which of course I loved about it.
The coupe is also an updated car, it has more sound deadening, the doors are heavier and less tinny mine is an April 06 so not sure if the later roadsters also got the facelift additions like the coupe. Funny I tried to sell my Z4Mc to Redline and the sales guy was like they are ok but they are super tinny.... I was like not really sure what your talking about but was talking about the roadsters. You also get the additional updates of the AUX jack as standard, glasses holder in the roof, bigger boot etc
I really disliked roadsters when I owned my coupe literally would never have entertained buying one. Its funny that the car was designed as a roadster and then they made a coupe because the car looks so natural as a coupe and has some fabulous design cues missing on the roadster.
Having the aero parts on the coupe like the skirts transitioning the lines from front to rear and the carbon fibre spoiler emphasising the lines from the bonnet over the roof and into the spoiler really makes the car, just simply stunning. The coupe really stands out with these mods and should have been standard. That and the addition of CSLs there just isn't a better looking BMW imo, those mods really make the car and the 5 spoke standard wheels are again another hate of mine think it makes the car look so much less aggressive and shouldn't have been the standard.
The roadster has a few strange decisions like the awkward key hole on the rear, the coupes boot opens by pushing the BMW badge and looks far cleaner to the point I think there was a group buy for body colour coded key covers

there is also less interior storage and the storage there is makes living with the car more difficult. Many bought the leather Z armrest which is a great addition but I think it does get in the way of the driving dynamic.
I sold the coupe to go traveling and when I got back and bought a 987.1 Boxster S and really didn't enjoy it as much as I thought I would. Everything the Z4M is is missing in the Boxster. It is so precise and predictable which if your into that is great but I like the axe murderer personality of the Z4M the Boxster is so difficult to step out of line and the fact it was 50+ hp down made it quite sedate.
What I did love was the top down experience so I sold that then bought a 996 C4S convertible as a project with my dad. This brings back that murderous feeling the Z4M has being rear engined, if you push it it lets you know! The noise is another level with the PSE which the Z can't come close too even with aftermarket exhausts. It is a little heavier which dulls it slightly but its a fabulous car at the time it was 20k with all the issues sorted so it was a no brainer. The car is based about 100 miles away and was still a project at the time so I fancied something I could drive regularly. The car I bought is a well known car on the forum rare combo being imola on imola and a good friend of mine Paul had it for sale and it was being sold on behalf at a garage for too much I think they wanted 17.5k for it at the time so I rang him and stuck a deal so ended up with another Z4M.
I was thinking about another coupe but when comparing the price difference the additional benefit didn't really make sense to me in the current climate and the fact I had already owned one so I came back to an Mroadster.
The other thing for me is the Z4Ms main draw is the value for money there just isn't much that will touch it but getting into 30k and rising your getting into more territory. Eventually I want to get into a 997.2 4S so the Z4M will probably be a 3-4 year car rather than a keeper depending on circumstances and space.
Love both but I wouldn't buy another coupe mainly because its just not worth the extra 10k the roadster just a great all round package. The MR is also a rare car similar to the coupe.
The other thing that I thought worth mentioning, I bought my coupe and it first was my first sports car and bought it straight out of uni. Back then they were cheap circa 2010 (middle of financial crash) mine had 40k was 4 years old and was only 17.5k from BMW. I sold it to go traveling then came back to other cars. The Z4M although again great for the money I haven't really gelled with it like the coupe probably because its a different variant of the same thing and I held the Z4M car high because of reminiscing, made lots of mates and had so many good times.
Ive also been lucky enough to have access to 996 4s/997 Cs/991 Cs etc and they are just such a level above that I'm craving getting into something better as there is a lot to love about the Ms but its also a flawed beast too.
Just one of those things I think you do grow out of cars its just current markets that make the next step a bit financially silly as prices will come down and people will loose money. The fact that you do need twice the money to buy a 997.2 and its better but again not twice as good just like the Z4Mc at nearly twice the money isn't twice as good.
There is also an element of just enjoying what you have, with all said and done every time I drive it... fall in love with it again.
BMW Z4M Coupe, Silver Grey, CSL wheels by
Tom Scott, on Flickr
Z4-forum Cumbria National Meet 2013 43 by
Tom Scott, on Flickr
BMW Z4M Coupe, Silver Grey, CSL wheels by
Tom Scott, on Flickr
BMW Z4M Coupe rear by
Tom Scott, on Flickr
Porsche 911's, Yorkshire Porsche Festival, Lotherton Hall, Leeds by
Tom Scott, on Flickr
Porsche 991, 996 Carrera 4S, Yorkshire Porsche Festival, Lotherton Hall, Leeds by
Tom Scott, on Flickr
BMW Z4M Roadster, Tatton Park by
Tom Scott, on Flickr
BMW Z4M Roadster, Tatton Park by
Tom Scott, on Flickr
BMW Z4M Roadster, Tatton Park by
Tom Scott, on Flickr
