I have 2 Consoles, 1 running 3.55cfw and 1 running 4.30.2 spoof 4.41... The reason I havent updated my 3.55 console, is because all my PSN games and backed-up games are already running under 3.55 so to lazy to refix them if i update
BUT if you have 1 CFW console, then no doubt 4xxx is better... Iris Manager, is pretty much a game manager without the BLOAT etc.. e.g. without the flash themes bla bla bla, game compatibility should be near the same. For me I love Multiman, oh and because you can use it as a file manager [haven't really played with Isis if it has a file manager or not] My suggestion? Well actually how I set mine up...
Install Multiman 4.40.x
Rename your games folder in Rogero using file manager [Multiman] and then delete Rogero. [Just incase it does delete your games] then transfer into the GAMES folder of multiman
Look for toggle_qa pkg., install it and then make sure you enable it
Then go with REBUG 4.30.2 CFW. You will need the original eboots to the games you have if you patched them for 3.55...
Thats all i can think of at this very moment
To Dual boot you will need a hardware like e3 etc