it all depends where in the rev range you putthe boost in.....
you can run a high CR (like the VAG 2.0 turbos of 10:1) but put the boost in at the higher end of the rev range, OR low CR and put tons of boost in all the time.... but that sacrifices low end driveability.
the way a supercharger works it puts "full" boost in right from the word go (unless its displacement) so if you have a high CR then its gonna be a bit of a gamble as to the lifespan of the engine.
oh and an overbore increases the CR too
