[Schwarzeritter]

I would just simply avoid the early 3.4's as they were known for issues.

I think it depends on what you want, I think the Carrera 4S is a pretty darn nice machine.

This is sort of a apples and oranges thing too me.
Do you want a NA car or do you want a boost car.
Both will have potential and different handeling charictoristics.

Ofcourse like most things turbocharged vehicles the performance upgrades are easier.
However there are gains things that the N.A. carries in favoriable driving charictoristics.

I remember that the 2001's + sell for a bit more as more updates were made too address those that the early variants 99/2000 had.