[Raptor]

Depends a lot on what the application is. If you are going to build a car more for street and DD and care less about maximum power, go with the 9:1 so you have better spool up and it is more tollerable off boost. Otherwise, there are arguments to be made for going with less compression as Shane mentioned. You can compensate for the lower compression with more boost and end up with more air in the combustion chamber (more volume), combined with long rods causing more dwell time at TDC to build pressure, which will create a lot of power. There are a number of other factors to consider as well, but there is enough info in this thread to get the decision made.