Should I get an internal wireless card or a USB dongle thing for my desktop PC?

Well, the time has come for me to move from my trusty Ethernet cable to the no strings attached magic of "N" wireless, since we're finally getting a new router upgraded from G.

My desktop is pretty far from the router, though, and the signal from the current router is kind of feeble up there. I hear N tends to have greater range, so are internal cards with their big antennas going to provide any noticeable increase in connectivity over those USB ones with their tiny, admittedly sleek form factors? I've got lots of USB sockets going spare on the back of the case, and I'm sure I can find room inside for a wireless card (basically the antenna is going at the back), so space isn't an issue here. I just want the best, fastest connectivity I can get.

I'm a bit lost on all this wireless stuff. I liked my cable. Knew where I was with that. But it's got to go, apparently, so any advice would be great :)