We have huge hate here in South Africa about CA18 vs SR20 in the SX/Silvia clubs

95% of the time the people that say CA18 is the better than an SR20 is people that have never actualy owned and driven an SR20.

Easy facts:
Stock on stock the SR20 has more power and a lot more torque
modified vs modified the CA18 turns into a bottomless pit of funding due to the parts being very hard to come buy and the majority of parts needing to be changed to support decent power levels.

I have owned both in 200sx's and both were changed out for RB25's... I have also built probably 30 11 and 12 second SR and CA's by now of which all i do a 1200km break in... in my 1200 I stuck with a built A series though if i did go CA/SR it would DEFINATLY be SR due to added parts availability and more power and torque at no matter what level of modification/investment.

You are swapping a motor to make more power, why not go for the one that makes more power and is cheaper to modify as well.