No way to tell now which game would be better to see. In October (and the Mets don't play much in October!) it's likely to be chilly at night, so you might prefer a day game. That being said, baseball under the lights is a great visual experience.

The Sunday game, being the last of the season, could have some sort of "giveaway" (hat, bobblehead doll, magnetic schedule, etc) -- the team will probably list their promotions in the next couple of weeks.

Try to sit somewhere between 1st base and 3rd base for best view. Down low is usually better than up higher, but opinions differ.