As far as I know the Garett spools up faster then the precision but the precision has more top end and mph.So lets say you have a big turbo and you don't have the converter to be able to get it to spool so you would use the garett to possible help out on the start.But if you have enought converter and are not having trouble getting it to spool up then you should use the precision.I would personal say the precision is the best choice,but as of right now I am still using the garrett and I have had no problems with it but when I am ready for a new one I will be changing to a precision to get more mph in the 1/4 mile.I sure there will be many more posts on this subject.Good luck