Probably the revision to the PS3 if only for the fact that the old fat was largely prone to overheat failures. Those old GT 7800 90mm's were notorious for failures and ran hot. I've got a PS3 fat that I saved, dropped firmware on, re-greased and everything and it's one of those I have to run with the fans at about half because of just how hot it gets...except in my case it's the CPU that's got runaway heat. It really is one of those that qualify for de-lidding but I'm afraid of breaking it so I just run it under 75C before the fans really kick in and pray for the best. It mostly accomplishes this so long as I don't do PS2 emulation. Once I do that, then it really starts to kick in.
Plus side is if I need that I have a PS2 slim that I have modded that I could just do with instead through ethernet. Not the fastest ethernet, granted, but it does the job better than USB 1.1 on the front for front-loading a bunch of ISOs.