There's not much difference between the systems. Though, I think I'd choose the 2nd system out of those. It's got faster RAM, and I like the ATI video card. Yes, the fermi cards are running a little hotter. The temp varies from system to system.
The ATi HD5850 will not get that hot, so i wouldn't worry about it. If you get the MSI ATi HD5850 with the dual fans and its out of your budget, I say go with a normal one and overclock that. Video cards were made to overclock!