Ok I have never owned a BMW, just don't like them, very common these days, used to be quite a rare site, now see one every other car, including the "M" classes
They are clearly very good cars, just not my thing is all but my concern would be in your confidence to enjoy its full 507bhp and the reason I say that is that when I had my Cayman S I had several "tail out" moments that were not planned

plus a few that were

Now it "only" had 296bhp and without doubt is the best handling car Porsche make........ and they know a lot about handling having mastered it in the 911
We mere mortals can't make use of these cars full performance, pure and simple

My guess would be that's why BMW gave the car the option to be run on lower power around 400bhp I think, as it would scare the s*it out of most owners in full fat mode
In step the RS4 as the clear choice, why? Well here's what I think:
As said above it is still faster than just about anything you'll ever meet (most faster cars spend their lives in heated garages, under silk covers - don't see the point

)
It is fast in any weather and rumour has it that it even rains in Florida once in a while
It's much rarer and this means lower depreciation and more exclusivity for you as the owner
It's big enough to carry 4 plus luggage in refined comfort.
You will have a warranty
Can you afford to replace a knackered V10
It's more economical than the Beemer (not that important I know but it's more in your pocket)
The M5 is fugly
It's not a BMW
Just my view on it but, did I mention, I don't like BM's so not an entirely impartial viewpoint........ sorry
PS I'm still right though
