just thoughts:

truth be told, football is probably better of the two in context of physiology i.e. muscle group and aerobic endurance (note...not anaerobic) as it's most similar to wrestling in types and duration of muscle involvement. some of you other coaches may be able to provide specific kinese information which supports/refutes.

personal experience does favor xc as the better of the two for pre-season conditioning...

personally, as long as a wrestler is competitive nothing really hurts. i'd support a kid in underwater bb stacking as long as it helped the kid. i'd prefer competitive off season sports as it helps build spirit of team work, self discipline, and a taste for winning...more so than just individual work outs