SR > RB if your talking about REAL POWER

SR is better in:
Cost of parts
Availbility of parts
aftermarket support

I lik the RB20 they are cheap, but my friend has one in his S13 and he has all kinda of problems with finding parts for it, and its crammed.

i personally like the RB25 for it price an the power it makes. althugh next year ill prob do an RB26 in the Silvia to keep it nissan