I'd take an M every time over an Alpina with the chavvy stripes and wheels that must be a nightmare to clean. Not to mention the EPAS, run-flats and open diff that Ms don't have, and that's before you get to the wonderful S54 screamer.
The lady doth protest too much, methinks...
Stripes are optional - most RS don't have them
Wheels are surprisingly easy to keep clean as long as you have something like a medium wheel woolies brush
EPAS - never found it particularly lacking for road use and I bet, if you didn't tell them, 99 out of 100 drivers wouldn't notice the difference
No run-flats - Michelin Pilot Sport were OEM
Open diff - easy to correct if required, I have the Quaife ATB on mine
Engine sound is a matter of taste and the Alpina has a hand-built engine with a tuned exhaust and it sounds wonderful, which is why you don't get Alpina owners hankering after carbon intakes, airboxes or exhaust backbox replacements to 'improve' the sound
On the other side of the coin, Alpina's don't require rod bearing shells/cams/followers to be replaced as preventative maintenance to stop them eating their engines for lunch or commonly have engine mount or vanos issues, have a lighter (to use) clutch & gearbox, they don't need to be worked hard to extract performance as they generate more torque at lower revs, have sensible servicing costs with no M-tax, get taxed as PLG so only £375/year - oh, and can easily average over 30mpg in mixed use.
As I've said on a number of occasions, owning an Alpina is like being a member of White's whereas ownership of an ///M is akin to being a regular at Stringfellows...