As far as I'm aware the 3.0 had criticisms raised at it on the handling/steering front, people I've spoken to have said as much as it's akin to a very quick 328 - no bad thing but not the M3 that it's supposed to be. And as such is relatively undesireable - still a very nice motor car though don't misunderstand me.
The 3.2 Evo model is an entirely different beastie,the various criticisms levelled at the 3 litre have been addressed and the 3.2 is more of an M class car.
Drive them both and decide for yourself I guess, depends on your driving style but you may find the 3 litre eminently suitable.
To sum the early models are less sought after but I don't believe to be particularly troublesome - check other threads/websites regarding VANOS concerns though would be my advice. I've read of VANOS wear at what can be relatively low mileage and depending on your warranty can possibly be not covered and an expensive fix.