[BiturboS4] ABT vs. MTM

[David]

Hello,
I'm planning to upgrade my 1999 Avant S4, and I'm thinking in two chipmakers
: ABT (310 hp) and MTM (306 hp). Since I live in Spain, I'll have to drive
plenty of kilometers to have the car modified (I didn't find any serious
engine tuner here). I'll have to go to Germany. I know many people in the
group have and enjoy the MTM chip. But what about ABT ? They look quite
serious to me, a little bit more expensive than MTM though, but they
definitely seem to know their job (their TT are leading the German DTM
championship this year). Any opinion ?
Should I consider a complete ECU change ? (Insurance companies and Audi
dealers are not very "chip friendly" here, and it could be a good idea to be
able to back up to the stock settings for the regular car servicing).
David.
A Frenchman living in Barcelona, Spain, 1999 Nogaro Avant.