I've had both styles, and for my preference, it depends on what you're putting in front of or over it.
For a red-dot sight, I PERSONALLY (no flame if you like it the other way) prefer full function A2 style sight like the DPMS or even better, KKF chopped carry handle (never had an LMT). The latter is more robust, gives you the choice of type of elevation wheel, and takes up less rail space. Although I have wondered how a DPMS rear would fare if you cut off the forward half inch or so and made it a one-screw job...
I've had 2 DPMS rear sights. On the first one, both screws were machined flat. They did not interface with the slots in the rail so you could position it anywhere on the flat-top. This latest one has both screws left intact and they each need a rail slot to fit in. I wonder if those broken screws were the older style like my first one. Screws with half of their post shaved flat can't be that dependable.
Now if you're going to use a magnified optic, then fold-down is the only option. I have only owned the #40, so I can't give opinions on any of the others.