I haven't touched my PSP in a while now since the fall that got its processor loose, but recently i took it out to play with it a bit, and i read theres now 6.x CFW that uses Official 6.x firmwares, or something like that.

I'm still using 5.50 GEN-B, and i was wondering if i should upgrade.

Whats the difference between the new custom firmwares? Which one should i install? I have a hackable PSP2000.
Theres the 6.60 PRO, the 6.60 ME.

Another thing i was wondering is if i'll have to install the Official 6.60 Firmware in order to install those new CFW. Will i be able to turn back to 5.50 CFW if i want to later?

Could anyone point me into the right direction?
Thanks in advance.