So what is the best 6.zz cfw to be on? Currently in 5.00 m33, not too fussed about poploader. 1st gen psp slim.
Well, 6.20 PRO can have permanent patch, but that's only really a benefit for unhackable mobos. With hackable mobo like yours you can use the custom IPL installer I believe, getting any of the 6.XX PRO CFWs permanent. I believe if you want to access PSN, it's easiest on 6.60 PRO, and you lose no features by going for 6.60 (all the PRO CFWs are the same) - you also gain no official features, other than PSN access, as Sony didn't bother adding anything.
Then there's ME - not sure what the latest is, but I think it's 6.60 ME-something.
ME has less features, but might have all you need.