Voted left side only for around $20, and left+rear for about $30.
Reason i chose left side instead of both sides is i'd want to run the line forward & down, then around to the asa (either front fitting or side fitting), like it'd be following a long trigger guard, but don't want the line to interfere with the mag release button, which is on the right hand side.
Rear is just nice if one wanted to run a line similar to a reducer, or put a gauge, although a gauge seems inconsequential unless one were fine-tuning the op. I don't plan on tweaking the internals, outside of running different springs in case the velocity isn't acting right.
Gas-thru-grip is a cool idea, but the amount of work & cost involved makes it impractical for the price point of the pump itself.