The 7 channel thing is a bit of a red herring when discussing the P12N. Very few of the existing P12N providers have all 7 channels. Brighthouse is one of the few, but it provides 1 channel on digital basic (in footprint), and the other 6 on its sports package. Dish came on board September of 2012, and they only carry a single channel plus overflows (available 120+ in footprint, sports package outside footprint). ATT UVerse took 3 channels, available on U300 in footprint, U450 outside, or sports package. The way the 7 channels have worked out in reality is more of an option package, under the basic framework of at least one channel on a basic tier in footprint, sports package (or very high level tier) outside footprint.
The biggest advantage the Big Ten and SEC has over the P12N are the fanbases. I used to live in the southeast, have a lot of relatives in the midwest, and now live in SoCal. I will argue til the cows come home that the PAC-12 has a great product, nearly the equal of the SEC on the gridiron. But the fans (on the whole) are not even close as passionate. Most fans of a PAC-12 team I know are bigger fans of an NFL team, and are okay with missing a few college games in order to keep Sunday Ticket. I don't think that will hold true with SEC fans, and DirecTV has greater risk of losing customers than what they faced with the P12N.
The SEC network also has the advantage of ESPN owning all games after CBS's single selection. The South Carolina/Texas A&M game would normally be on a primary ESPN channel, but ESPN can move some good games to the SEC network to make it "hurt" more if you don't get the game. I am curious if there will be a bait and switch once they get providers on board. Will they move those type of games back to ESPN/ESPN2, or will there be some guarantees to the providers on how many "good" games ESPN will put on the SEC network. Be interesting to watch it play out.
Like I've said, there's a lot of speculation about what exactly the points of dispute are between Directv and Pac 12. No one knows for sure, and whatever people connected with Pac 12 or Directv might claim isn't necessarily true - they aren't under oath and can say whatever they want to try to improve their negotiating position or make people believe the dispute is the other side's fault.
That's a good point about game selection and the SEC Network. The B1G showing games on ABC/ESPN and BTN means BTN always picks last, and often really messes up the schedule (sometimes you see four games with a noon/11AM start time, and only one at 3:30/2:30, and there's never a BTN game at night, because it appears ESPN's deal means they have the right to have an exclusive on a single time slot for the conference (at least that's what us B1G fans have guessed based on how often this crap happens now since BTN was created)
With one network owning everything they can spread SEC games around better, and as you say, make it hurt by putting some big games on SEC Network right away. There's a lot of people who think that when the B1G's deals come up in a year or so, they might switch from ABC/ESPN to Fox for similar reasons. Though of course, they'll have to willing to pay more....college football is all about money now, right?