the small goal should be able to hold 9 or 10 balls and still be able to cap (I say 9 and still "safely" cap, Lavery says 10 - so when in doubt, I guess you'd go with the rocket scientist. Not gonna win many disagreements with a guy who actually fits the "rocket scientist" cliche)
I don't remember the large goal exactly - but I think it will hold about 16 and be able to cap safely, probably + or - 2 balls depending on how they fall and position in the goal.
Hope that helps.