It depends on what you're breeding rabbits for, as to which ones you'd keep and which ones are culled from the herd.
There's several different methods of culling, too. I have a friend who will eat any rabbits I don't want. At some point I may swap two rabbits for one back ready for freezer camp, but he lives too far away to go home, process the rabbits and then bring one back. Hmm, maybe he can stash it in the freezer and bring it back frozen later. But, in any case, he's willing to take any and all rabbits that aren't destined to be sold.
If I have excess rabbits that are good rabbits, but don't fit into my herd, then they get sold to folks who want to keep them as fiber bunnies. I only have angora bunnies so they're kinda like micro-sheep and not pets at all. They've got the temperament to be a pet (AFAIK, temperament is genetic and is a main selector when deciding which bunnies to breed) but their coat maintenance is too much for most kids so the bunnies are usually only sold to folks who are going to spin the wool.
As for culling policies, it mostly has more to do with available space than anything else. There's only so much bunny space here and bucks need to be kept separate in their own spaces so that really limits the amount of bucks I can keep here. Females can live in a big communal hutch so there can be up to a dozen of them all together with minimal problems.
I usually have between two to three dozen angoras and they are here to provide fiber for Hula Bunny yarn. Wool quality and color is the primary selection factors. There's three standard colors of Hula Bunny yarn - 'Coconut Dream' (creamy white), 'Moonlit Dance' (silvery gray) and 'Beach Bunny' (pale tan). That's in order of popularity of yarn, so I generally try to have the colors sorted with the most whites, then blacks/blues/lilacs/agouti and then fawns/torts.
After choosing for wool quality and color, the selection criteria are temperament, health, conformation and level of inbred to the rest of the herd - especially with the bucks. If I have a really nice buck that there just isn't room for in the herd, I'll try to find it a home somewhere nearby so I can borrow him back at some point, hopefully. Although once a rabbit is out of my hands, no telling what can happen to it. I'd been selling the best excess stock inexpensively to someone who was setting up a 'reserve herd'. They were sold inexpensively so I'd be able to access them later, but they weren't a very good bunny owner and the bunnies all got eaten by a band of roving dogs last month. So much for being able to get those genes back again. Sigh!
opcorn:
