For me I am training three 6'8, 6'9, 6'10, and 6'11. I got three main trainees I drafted and three other suitable trainees. In my case I'm doing one on one forwards or pressure training for the time being.
I think it does not matter what you train. Just keep in mind that your trainees usually lack skills. So a lot of times its best to focus your offense around your better players either inside or outside focus.
For instance, my best trainee is a 6'11 Superstar PG. He probably won't convert to inside skill training until he is 20. But at some point he will make a great PF/SF.