If you're going to do a partial boil and then spit the batch into mulitple fermenters, make sure you either split it up evenly before adding the top off water, or mix the wort and the top off water extremely thoroughly. It may seem mixed well even if it isn't, and you'll end up with one extra light beer and one heavy beer. As far as the yeast goes, just use a proportional amount, ie 1/2 as much yeast if splitting the batch into two fermenters.
One advantage to full boils is that the lower specific gravity of the boil results in much better hop utilization, which is very helpful for IPA's and hoppy brews. Another advantage to full boils is a better hot/cold break, resulting in better clarity.