Hi, this is probably an old question but, what do the A-, A and A+ ratings correspond to? What is the variance between each rating? Also should I pick a 19 yo A+ 4 stars potential 6'4 PG over an 18 yo A- 3 stars potential 6'6 PF? Will the extra season of training for 18 yo outweight the A+ rating of the 19 yo? Thanks for the help!