Well any you would have to choose no one can give you the best CFW as everyone's opinions are different but if I were you I would stay the safe way seeing as you only want to mod just install 3.55 CFW then install anything up to date like Rogero or Rebug. If you decide to remain on CEX (Retail CFW) then install CCAPI and your good to go.
But while your on 3.55 if you haven't already install a CFW and make several dumps of your NOR from your E3 just to be safe. There is nothing worse than not having a dump as a fail safe incase things go terribly wrong.
Should be all you need really just be careful when going online as you will more than likely be banned so take care.
Use things like PSNinja to remove your history before going online to reduce risk a little.
Oh and check the MD5 before installing a CFW just incase someone renamed a OFW to look like a CFW then you would be back to stock.
And whatever you do DO NOT USE A MAIN ACCOUNT!!!!! I can't stress that enough because if that is banned you lose everything you have bought.
I myself am on Rebug 4.46 Rex spoofed naturally