My rig has 3 slide outs, 2 in the rear (one either side) and a big one in front.
I like the front slide to be on the driver's side (mine is) as if it's on the entry side it tends to take up part of your "porch" area as it were
Another issue, if doing the Wall-mart bit, I prefer to park at the far edge of the lot (as far out of the way as possible) with only driver side slides I can put them out (over the curb /grass at edge of lot) and not take up more parking spaces,,, They are also safe from passing vehicles (since they are not in a traffic area) with the 3rd slide (which is my bed) I don't feel comfortable doing that
Slides are nice, means extra maintance (more stuff that needs it) but worth it