I havent used Ultimate the 3.70 spoof wont allow you to play games above 3.56 its just mainly for PSN access which is iffy at best. Kmeaw seems to be the most popular and stable and ultimate is rather new. As far as multiman just use the lastest one which i think is 2.09.02, but first install 2.09.00 BASE then update to 2.09.02 or it wont work, also you need to install BDEMU2.pkg after you install multiman to get backups to work. That should be it.
PS3 Slim 4.21.2 Rebug REX 4.31 Spoof (external 1TB/3TB), PS2 Fat w/ Internal HD