Neither - go Microtech
someones selling one here: http://forums.skylinesdownunder.co.nz/show...&threadid=18058
Reason for this is, if you're trying to push out those figures you'll need to change a few other sensors, and at 350rwp you'll need to either upgrade to a z32 afm, or go for a diff ecu, such as the microtech which runs on it's own internal MAP sensor
Power fc is just a drop in replacement, so runs off of the std factory sensors. Allows big tuning but the sensors are still the same and will need to be upgraded
s-afc is only an AFM interceptor, it adds or subracts a small amount of voltage and tells the factoy ecu this, so that you can tune the mixture a little at each load point
I'm pretty sure that you can't put a MAP sensor or anything else, to by-pass the AFM, since it is requiring an AFM signal, and the two aren't in a proportional relationship (ie - not compatible)
otherwise you could run a haltech or microtech in piggyback with the factory ecu, so that you have the new ecu controlling fuelling and spark and the factory ecu controls the idle and air con etc - if cops look in kick panel it shows std ecu, but factory ecu only controlling the basics
they're all good though, just depends on whichever one you want to have
also I think s-afc's are 512 bux from nengun, but can't be bothered looking as 56k dial up is pissing me off