First engine build question
The difference between 9:1 and 9.5:1 is 5-10 hp not enough to worry over.
It is not in the peak HP which is all that number means; I sure wish folks would get away from that stupid HP vs CR Wallace calculator (which is not accurate anyway). It is totally misleading as to the outcome of SCR/DCR changes.
The operating difference for DCR shows up in the low RPM torque. Anyone with hot rod sense will indeed feel a difference of .25 point of DCR in everyday driving, in terms of throttle response. 0.5 point will be noticeably quicker taking off. A full point of DCR makes the engine a very different animal.
So, for a street engine, CR IS quite worth worrying over, as well as forsome racing disciplines. Drag racers just work around it with high stall torque converters, etc., but that is not what works well for a road race car or rally car, where the wider torque band, extended down to the lower RPM's, is very much needed.... or for some street usage if you don't want to rev to 2500+ RPM just to move away from a stop sign. (Though some people may like that LOL)