This is a close one. When it comes to protecting the quarter back, both lines do a very good job. The Bengals are 3rd in the NFL and have allowed just 29 sacks, while the Chargers are 4th with surrendering just one more (30).
It should be noted that in the last 6 games, the Bengals line has surrendered just 3 sacks and have held the opponent to 0 sacks in 4 of those games (including 0 sacks and 0 QB hits in their week 12 matchup with SD).
However, the run game is why I give the Chargers the edge. While they only average 13 more YPG (122.8 to 109.7), the Chargers running game has improved of late. In the month of December, Ryan Mathews led all running backs with 534 yards.
Though I don’t see this as a huge advantage, the Chargers are more consistent across the board and the 2 game stretch where the Bengals gave up 10 sacks (Mia and Balt) is still very fresh in my mind.