I'd go for the first guy, both aren't really what you're looking for so I'd try to get a trainee in another way at some time (next draft or market). In the meantime you can train the first guy who has a lower ceiling, but you probably won't hit it (nor that of player B), because I think you should get another trainee before that time. So if you're consider you will get another trainee before either caps, it's better to take the one with the better starting skills so you can have a decent bench player or sell him (good 10-20k players sell nicely).