I spoke to someone at a pumpkin farm in New England last year, and she said they grow mammoth ones to pull the crowds in come Halloween... but the little ones (football-sized downwards) outsell them by weight by a factor of four because they're easier to cook with. This is because once cut a pumpkin doesn't last more than a couple of days at room temp, but uncut they last for months especially if you leave a decent "neck" on them.
She also said that she uses the same variety for both - if you nip off all but a few pumps you get giants. She also said that if you do this, the overall yield is lower.
So in true SS spirit, this year I'm going to grow two giant pumpkins - one for the kids and as a spirit lantern (pagan tradition to place a lit lantern facing west to invite the spirits of the dear departed into the house), and one as a backup in case of accidents. The others I'll allow to set as much fruit as they want - until I run out of old roof tiles to set them on, that is.
Check this out!
http://www.extremepumpkins.com/