LaRue and Daniel Defense, in that order.
The DD tube is a bit lighter weight. The LaRue has four true 1913-spec rails. The DD rails at top and bottom are 1913-spec, but the sides are not. That shouldn't make a difference when mounting things to the rails, but I mention it because it gives the LaRue rail a rounder profile while the DD is a bit slimmer (more of an oval shape).
I have some of both and like them both. The LaRue does have a locking "key" to prevent the handguard nut from working loose. If you torque the DD handguard nut properly it shouldn't work loose. That said, I do like the key on the LaRue. It also help make sure the tube's top rail is aligned with upper's rail.
The DD is a two-piece tube that is welded. The LaRue is made from a solid piece of aluminum.
The DD rail comes with some rail guards or covers. The LaRue does not.
You won't go wrong with either.