PS3 - will be good for Graphics, lots of RPG titles, and blue ray player for the home (mainly 1 player games)
Wii - will be good for innovative gameplay, something easy to pickup and play (easy to get your girlfriend into games), awesome multiplayer/party games, more titles that will define the system an be reasons to get the system, and cheaper games ($49)
plus i'm not quite ready to dish out $600 for a console. Id rather just upgrade my computer.
consoles should be cheap and good for gaming in small time periods (30mins -1.5hrs)
heres a good article about why the Wii will be great :