NOPE there is no physical difference. CB or WC just take it. I would rather get a CB than WC as the WC are more sensitive and can die easily, especially when young. With WC there is also a chance that it may not have a perfect barbels.
Basically, most of the one's you're going to find are WC. Not very many people breed silvers, they're not worth it for the little profit they bring in.
check out snookn21....i got one from him that was really nice @ a good price....not much diff....even wc get de. id get a jar or a blk aro....asian if i had the chance.
I,ve had 2 WC silvers both got drop eye on one side but the one from Venezuela had much more orange highlights on the fins then the cColumbian. I prefer wild caught because less chance of inbreeding and ususally coloration is better