I generally agree with Keenan again. Standing closed guard breaks are largely more effective.
The only thing I would add is that I feel there is a time and place for techniques which are less effective. That is when I would use the knee in the butt method.
If I'm down 2 points, 30 seconds left, in closed guard -- you can bet I'm standing up and doing Keenan's way. It's the fastest and most effective way I know of to open the legs. And I need fast and effective in that situation.
If I'm up 2 points, 30 seconds left, in closed guard -- I am probably going for knee in the butt here. Why? Because I can keep a more defensive posture vs standing up. That minimizes my chances of getting swept or countered. I don't need fast and effective here; I just need safe and defensive.
And that's from a purely competition standpoint. The truth is I can't even remember being in closed guard in competition for a while now. It is not a common situation these days. Most guys are playing open guard in my division at least.
From a day to day rolling standpoint, I might need a breather after rolling a bunch of rounds in a row. A slow, deliberate knee in the butt break might be appropriate here. It still works for me often enough. Even if it doesn't work, I've still gotten my breather. I can always switch to a standing break then. There's no rule that says I can't switch strategies in the middle like that. I often do.
I don't like being too dogmatic about techniques. If you would have told me five years ago that no gi sub only would end up being almost exclusively going for leg locks, I wouldn't have believed it. It probably won't be like that in another five years either. But as for the present day, here we are. So I try to keep an open mind because things definitely change. I just know I can't predict the changes so I might some techniques in the future that don't work quite as well right now.