honestly i think alot of what FIRST uses each year has to do with cost/availability for both themselves and teams. pretty much since the floppies things have been commonly available. playground balls, soccer balls, plastic totes, playground/exercise balls, PVC pipe, etc. they need to make it so that everyone has access to them.
as far as balls go i would love to see balls on a different, like golf balls. can you picture 500 golf balls on the Field at once, yea it will never happen because field reset would be ridiculous but...just think about it
