Undeveloped - Have sold stuff.
Pro: Easy to use. No approval process. 9% Escrow. You have insights into your traffic from Analytics
Cons: Not a marketplace, so you have to rely on generating your own traffic (type-ins, promotion, etc). You have to create your own logos (if you choose)
SquadHelp, Brandpa - Have not sold stuff.
Pros: They create logos for you. The drum up the traffic for you by buying ads. It's a marketplace so theres a greater chance of people stumbling on your name.
Cons: Approval processes have no rhyme or reason at some of these places (Brandbucket especially) Commission fees are insane, like 25-30%.