This, right now, looks like a win/win choice. I think all of the guys you mentioned have good potential for big games.
Drew Brees is the better QB, hands down. He is still the focal point of the Saints offense but his match up is definitely not as good as Flacco's. At the same time, look at the three opponents that GB has faced so far. Alex Smith only threw it 26 times. Cutler had 27 attempts. And Wilson had 21. Brees will likely have 35 attempts, if not more.
Looking at Flacco's situation now..the Browns have allowed opposing QB's to throw over 30 times and multiple TDs in every game. BUT Ray Rice is still the number one red zone threat for Baltimore.
Now for the TEs. I like Pitta this year, but Gates is still Gates.
KC has allowed a TE TD in each of its games this year. Gates has not registered a TD in the two games he played, so he has to be hungry. Just keep tabs on his rib injury in case he can't play.
Pitta faces a Brown's defense that has only allowed one TE TD this year but they haven't really faced a TE that is as involved in the offense as Pitta is since Celek in game 1. Pitta is number 2 in the league for TE targets at 30. (Jimmy Graham has 31) Pitta has had atleast 5 receptions for 50 yards in every one of his games this year. He has two TDs.
Taking all of that into account, I'd go with Brees and Pitta. Elite QB and hot hand TE. BUT the Flacco/Pitta connection is a decent boom or bust play as well.