I think neither the 4GB 360 nor the 16GB PS3 are for online gamers. So XBLA / PSN titles don't matter that much to them probably.
But the singleplayer experiences for quite a few PS3 titles require an install of 3 - 5 GB. The system will take its storage too. Just play GTA IV, MGS and 50% of the storage is gone.
Imagine not having GamePass on your console...







