Houston's run defense has gotten a lot better over the past 5 weeks, and is no longer one of the worst in the league. That, and their pass defense isn't elite, so Peyton Manning will be throwing quite a bit.
Also Donald Brown should be OK to go, which means Addai won't be all by himself back there; not that he did anything with the carries last week...
As for Jacobs, I second him being "the man" this week. The Chargers are 27th against the run, and Jacobs is due for a big game. He has 12 more carries than Ahmad Bradshaw in the past two weeks, and the shaky Eli Manning just can't be trusted. The Giants will run the ball a ton of they can get it going.
Gotta go with Jacobs.