At this moment in time you will probably be looking at a car @ 10 years old, so condition / maintenance will be the paramount importance. The Twinnie rear suspension issue is easily solved , use the 3.0 rear pans etc. The Cambelts don't tend to fail IF
they are done ( along with variator ) every 3 years / 36,000 miles, but the twinnie can have a considerable oil thirst.
The twinnie takes a bit of getting used to to get it going but once there corners like a go kart.
The 3.0 tends not to chew it's diff / gearbox ( for some strange reason the 147 flavour of GTA does more often than the 156 , weird ). BUT the Q2 absolutely transforms the 3.0 handling,
no washout on corners, the more power you give it the tighter it pulls you round , just don't lift off at the limit !
I am prejudiced but that V6 pulling you along is an unmatchable experience. Ours did 4,000 + miles for "the" birthday party, returned with oil still golden and still sitting on max.
If you can afford petrol / insurance my vote would be 3.0
Good Luck in your hunt