the non evo (3.0) has a single vanos
the evo (3.2) has twin vanos
both cars can suffer vanos problems, but it is quite rare now to get 1 that has problems.
The 3.0 is the quicker car upto 100 mph and the evo will leave a 3,0 after that point, I would have either tho as im not that fussy
as for the E34 M5 I seriously hope your wrong on that front, as I have had one and whilst I thought it was a nice car, I think I did the right thing in selling it to get another cossie.