Looking at the contents of the zips, PPX also includes CrossBreeder and CB's entropy engine, which is superior to rngd that FOM uses. On that basis alone, PPX would be better. But that's not a fair comparison, so we have to remove everything CB-related from the zip.
We're left with /system/usr/idc/mxt224_ts_input.idc in PPX which seems to be a touchscreen responsiveness tweak, but I don't think this works on our device, because we don't have that file, but you can try...
Then you have to compare the init.d folder. The scripts inside both of them are (mostly) redundant if you already use V6 SuperCharger, and do more or less the same thing, and some scripts are even shared among the two.
The only two scripts that could maybe make a (very tiny) difference are 98fly_engine in FOM and S98system_tweak in PPX, and you could probably run both of them together, but maybe they will conflict, I don't know, and anyway even some of the tweaks in there are redundant if you use V6...
I'd personally recommend flashing edited
FOM and nothing but S98system_tweak from PPX to see how they work together, and then CB on top.