Sell old phones with custom rom or flash back to stock?

[cardboardbox]

I have some extra old phones that I should probably sell to help pay for newer phones. Should I flash back to the stock rom or leave it with a custom rom, or maybe flash to the newest version of a custom rom?

Since the custom roms are better I'd rather not go back to stock but so far I havent been able to provision my TP without going back to stock and I wonder what a potential buyer will do with a phone that cant be provisioned. Its possible they know more than me so maybe its not a problem.

I've tried ##786# and ##778# and neither do anything in a lot of roms like Energy and Swinn. I've tried the sprint provision cab in Energy but it doesnt fix the data problem. Nothing I do fixes my lack of data except for flashing back to stock and using the update profile option.