I'm assuming the part that is installed on the HD is the important data it needs to load for play. The reason they do installs is to avoid BD access. I normally don't buy DD versions of full games, so that should not be the biggest issue (I have Warhawk, ACiI and Wipeout HD). I can't install everything and leave it and should not leave demos installed. That being said 110GB (maybe less) is not much these days.
Edit: I went with the Momentus XT 500GB, got it for under $100.
Now playing: Madden, Diablo 3, First Light, PvZ: GW
Recently Finished: Watch Dogs
PSN & XBL: Scuzzlebutt33