Heres a comparison i found in a mag.
SR20 - Garret GT28 b/b turbo, ARE intercooler/stainless intercooler piping, 3' custom SS exhaust (inc 3' cat), SS Manifold, Standard ECU
Result - 208rwkw (280hp)
RB20 - HKS GT 25/35 b/b turbo, ARE intercooler/stainless intercooler piping, 3' custom SS exhaust (inc 3' cat), Standard ECU
Result - 203rwkw (275hp)
Im not sure what model SR20 this is as its got painted rocker covers, id suspect a later model simply because 3/4s of 180s do not have their original engines... but its a comparison!
Shows the RB and SR make very similar power as the SR has a manifold and slightly more power. Ive always seen them make very similar power! As i said before if you put an rb25 turbo onto an rb20 then it may compete with the s15 (sr20 using t28) alot better (even though the s15 also got vvt), however Nissan decided due to making the r33 a boat (even more so than the 32 that is..) 500cc and more compression was needed But thats another topic all together! hehe