Like others have said, for me, price is the main consideration these days. Pandemonium can descend at either airport if you're unfortunate to land the same time an another flight.
Have done both, think MCO is set up better, has more to do and is a bit more modern, has the benefit of Magical Express as well.
I would however, recommend Sanford over MCO, have got through there a lot quicker, has a decent duty free on the way back, and an excellent kids club that saved us when we were delayed for 8 hours coming back last time round. Get through Homeland Security a lot quicker than at MCO so any location advantage is often negated - but to be honest, you might as well flip a coin!