In the end, there are only three reasons to choose:
1) Hard and fast association rules (which you should know about BEFORE choosing to participate;
2) A hard-nosed coach/trainer who insists on one over the other;
3) A parent or kid concerned with overload.
Where coaches, trainers, parents and kids are honest with each other and TRULY have the kid's best intertests at heart, this is not a problem.
