Upgrading from 3.55kmeaw

So I currently am running 3.55kmeaw. I've been out of the scene at least a year and a half.

What im trying to figure out now is if I should upgrade to REBUG 4.30.2 D-REX EDITION, REBUG 4.41.1 LITE EDITION, or 4.40 Regero.

I've been hearing more praise on the REBUG versions, but I don't get the differences between the 3? And also, although I don't think I'd want to go back to 3.55kmeaw, I want to make sure that whatever version I upgrade to, I still retain the ability to downgrade.

Any help?