I inherited an iphone 3g and it's still at firmware 2.2.1. It will need to remain unlocked and jailbroke so what firmware is the best to upgrade to and which program should I use.
Welcome to MMi,
If you look in the "Guides" section in the top gray header bar, a bunch of options are there.
You can update to whatever firmware you want, jailbreak and unlocks are available for the 3G.
I have read alot on this forum already but nothing specific to my situation. I'm still not sure which version to upgrade to or if I should upgrade at all. Is there any benefit to upgrading from 2.2.1 version?
App compatability and features are the main reasons for upgrading. Don't go any higher than 3.1.2 or you will upgrade the baseband and lose the ability to unlock.