The GT760 has a fixed lens, therefore, no zoom. You have to set the projector exactly where you want it for you screen every time you set up. Here is a quote from Projector Central's review "Image Size and Displacement: The GT760 can put up a 150" diagonal image when placed just 5'5" from the screen. At that image size, the bottom of the image is offset about 10" above the centerline of the lens, and this is a good displacement for tabletop mounting. Since the GT760 has no zoom capability, a different image size will require moving the projector."
Unless your screen and projector placement is permanent, adjusting the picture size could be a PITA. If for that reason only, I would get the 730HD. As for the BenQ, if you have 2500+ lumens, you can light up a pretty big screen. I have an Optoma HD66 (2500 lumens) and it shows very nicely on both my 120" and 130" screens.