90 Quattro generational differences

[Wayne Dohnal]

This is my first post.  If what I'm asking is in the archives, please give
me a gentle hint how to locate it :-)

I'm looking at used 90 Quattros (5 speed), and I'm wondering if I should be
seeking out or avoiding any of the three generations.  I know that the 20v
has more power than the 10v, and the V6 has more power than the 20v, but
that is not necessarily my primary concern.  Can anyone address any of the
following issues for the different engine configurations?

- reliability
- ease of regular service, like oil changes, air filters, fuel filters, etc.
- ease of service for more major items, like timing belt, water pump,
starter, power steering pump, etc.
- are the clutches and transmissions basically the same ?
- are there any other issues with different generations I'd want to know
about?

Thanks!
Wayne Dohnal,  Banks, OR.