F900EX
Flown properly, there's no reason why the engines shouldn't go all the way - with engineering tweaks and pilot education improvements over the years.
I'd say go for youngest if you can, but above that, go for the machine that's been the best cared for.
This article may help give you a good overview - a few years old now - but still very relevant.
http://www.avweb.com/news/usedacft/182792-1.html
The PA46 is a fabulous aircraft - it's firmly at the top of the GA single piston fleet in my view. It's got speed, safety, style, space, comfort and the utilitarian luxury of pressurisation. Once you've had that, there's no going back. Those twin turbo chargers - power - will be more than at home in Colorado too...