@King_Louie , you won't hear any arguments against the Xvo from Kat or me, and if you need the money, yes - sell the BB.
My reasons for hanging onto the 3's are strictly around the durability, given what's at stake right now. But again, bills come FIRST.
The "a" (as in Rev 3a) simply means that it's an anodized finish. The original BB's were raw aluminum (aka aluminium), and required a MUCH greater amount of attention. They're marvelous, in fact I'm using one currently, but they require thorough cleanings (alcohol & olive oil) OFTEN. When I was using it almost exclusively, those cleanings were weekly.
If you didn't do that, the door would end up getting stuck on you (due to oxidation). And trust me (been there), that's NO fun.