Yeah, the power is definitely a no brainer, but on the other hand having played games like Arkham City and Borderlands 2 with hardware PhysX enabled they look quite barren without it. It's weighing up whether prettier graphics are more important than vibrant interactive worlds. I keep deciding on one then changing my mind the next day! If only the 780m was in my price range haha.
Mine will be a replacement for my older 17" Clevo x7200 based laptop. Even the 17" will be half as heavy that thing! It's a beast and not at all pleasant to use on my lap. The sheer size of it makes my want to use a smaller laptop and the 15" seems about right. Then again when I'm using it on my desk the screen may well be too small next to the 21" monitor.
Space is always a problem for me haha. My current one only has a 64gb SSD for the OS and a 500gb HDD for the rest. The SSD keeps getting full up by programs refusing to give the option to move their data out the user folder, particularly whenever iTunes updates it finds a new way of filling it up when it backs up my 32gb iPad without even checking if there's enough space, I've currently got at least 3 symlinks set up to combat just iTunes. My storage drive keeps hitting the limits from music, videos, development software and games, so I'm constantly having shift things around, delete games and so on. In the new machine I'm going for a 256gb SSD and as big a HDD as I can get, or if I go of the 17" 2 of the biggest haha.