I think most people would agree that the 12 team, 2 division format has worked really well for the SEC. I am of the opinion that 16 teams with 2 divisions of 8 stretches your inter-division and non-conference scheduling too thin. With 6 team divisions you play 5 divisional games and 3 non-division games (2 rotating, one permanent). That leaves you room for 4 non-conference games while playing against 73% of your conference. The most infrequently you would play a non-divisional opponent is twice every 5 years.
Now, if you have two 8 team divisions you are stuck playing seven divisional games. Add a permanent opponent in the other division, and you're already at 8 conference games. To match the two rotating inter-division games of the current system, you'd have to drop two non-conference games. And that still leaves you at playing 66% of your conference. You'd play certain teams twice every seven years.
Limiting yourself to two OOC games as opposed to four is a big deal. First of all, you're probably losing a home game, possibly two. That's lost money. Secondly, you're limiting your options for premier non-conference matchups which is a bummer for the fans. You also lose the chance to schedule cupcakes. These make your path to going undefeated easier, but they also provide important opportunities to give young players and backups experience.
Expanding to 14 teams does stretch your schedule, but not as much as 16. I think it's a better option for the SEC. With the PAC-x and possibly the Big 10 moving to 16 teams, I don't think the SEC wants to stay at 12 simply because they would be seen as being surpassed, upstaged, and outdated. But I don't think anyone will make an issue of 14 vs 16. The other benefit of expansion is additional TV markets for more TV dollars, but you also have to divide the profits more ways. Going for more quality in the schools we expand with rather than quantity will be a good move.
In the case of the PAC-16, the 8 team divisions will probably work out alright. You basically have two separate divisions with little shared history/rivalry. They can afford to forget a yearly interdivision game and probably don't care as much about how often you play teams from the other division.