The 911 is a classic, with classic looks and incredible performance for every day use. I generally think the 911 is one of the best looking cars ever made, and to mess with it is sacrilege. There isnt really another car that has the same appeal. How ever good the Z4M is, it doesn't quite cut it with the 911, having access to both it gives a real world comparison.
Stats only tell you half the story.
The 911 is just a great car to drive like nothing on the road. The Cayman I test drove before buying the M and for the extra 5-10K that it was... I found it pretty boring tbh, great car just boring and the fact it does look like a boxter with a roof just doesn't have the appeal... The 911 is exactly that the real deal and Porsche wont enable the cayman its real potential because of that. Would be a 911 every day for me, cayman or boxter wouldn't get a look in. The M in BMW terms is the best you can get... a boxter is entry a cayman if you want something with a roof and 911 is the pinnacle of the brand.
If you haven't driven one go drive one. The Z is a great car which is why I bought one, but the porsche is a different breed altogether. Its like an event driving it everyday, feels special and similar to the Z a bit of a handful unlike the cayman and boxter.
It is true tho, value for money is questionable. But the reason half of us have Zs is because they are cheap now, The 911 is a different territory and priced accordingly I suppose. But there are great 911s out there, 40K will buy you a very special one indeed, and 40K IMO is a price worth paying! Awesome cars.
But if you are used the the M then the cayman is a very fast but a soft version, most will be disapointed. There is a reason most of us went Z4M because its a niche within a niche perfect for very few people. The Cayman gives you too much confidence and that for me is a no no, lulls you into a false sense of security, then you drive any other car and end up in a hedge. I want to feel like im driving it, not that its driving me and thats where the appeal is. The 911 for me is the only upgrade from the Z4M.
On a side note the 911 rides better than any M I have driven.
I am talking the more modern 911 as thats all I have had experience with, 997 MKI and MKII. Although I test drove a 996 C4S which apart from the turbo and GT3 would be the only 996 I would buy. It sounded and drove really well and I loved it, I have a real soft spot for the wide body 911s and I always wanted a 996 C4S though it was the best looking 996 by far but the Z4M did offer better value for money, for a half decent 2002-2004 C4S your looking anywhere between 20k for a poor version and 30k for a garage queen. THe Z4Ms a good one is 16-18k and about 3 years newer a full BMW warranty and newer tech in the car which is also important. The Porsches do cost money to look after but as long as you know the faults and how to remedy them there is no issue with buying them, JUST LOOK AFTER THEM! Thats the real problem people buy them and dont look after them properly, which means issues for you. The BMW will get away with being treated pretty rough but the Porsche doesnt needs care. TBH when I have a bit more spare cash I will jump to a 997 C4S or a Cs. The Cs we have right now is a riot.