Either way, although if 1/3 of the water puts you in a good mash ratio then you'll get better extraction from having two larger sparges.
Having said that, I generally use as much water as possible for my mash, and only sparge with what won't fit. With my MLT I can do up to 3.5qt/lb so I'll only have a gallon left for sparge. Its more like no-sparge this way, but I still get my usual 75% efficiency.