shorter intercooler piping if compressor is on drivers side.
actiondan used to make alot where the comp was on the passengers side and also able to retain aircon etc. and depends how tight the exhaust will be to the x-member
if your getting a custom manifold done, just put it exactly where you want

there are pro's and cons of each that will determine how other things are done. if you mount the comp on the drivers side, there is generally not enough room for std oil filter (with bigger turbos)
also think about the return, you can only mount a turbo so high with the compressor on the drivers side. just make sure you can get the filter piping on, but also have enough height for return, (not so much of an issue with compressor on other side)
umm hope that helps.