The great debate. I have run both this past season and seem to like the mod chamber a little better. There was by no means a huge difference in the 2, but the feel was slightly better to me w/ the mod chamber. I run an 86mm Dominator flattop motor @ 210 comp. that hits 7200 rpms w/ a mag pump. I have a Blaster mod chamber as well and have tried it on my ported otherwise limmitted set up vrs. the SJ mod chamber and saw gaines at bottom slightly, but seemed to run out before the mod would. No huge difference here either.
My choice would be the SJ mod chamber on both my setups not so much due to power only, but due to power / ease of maintinence too.
I have been runnin a 2.5 n/s in my stingers w/ no problems.
Just my opinion, I am by no means a roll model or professional though.