The LE Tactical and Elite LE Tactical have 16" HBAR barrels. Technically there is no 'need' for a brake, because they are of the legal length. The XM15 E2S and I believe the MT6400 will show a brake, because the technical length of an M4 profile barrel is 14.5", which represents certain legal issues (barrel length must be 16", barring certain specific circumstances). It's also done to retain the 'look' of the flash hider. In order to make the firearm legal, a muzzle brake is attached to put the overall length to 16" inches. Note however with the Bushmaster that you can opt to get a full 16" M4 barrel with no brake, if you so prefer.
One of the big differences between the RRA and the Bushy would be barrel weight. The RRA's use if I am not mistaken a Wilson HBAR barrel. The XM15-E2S-M4 Type uses an M4 profile barrel, which is rather lighter than the HBAR....to some people it makes a difference, to others it doesn't. YMMV I guess.
Basically put, you really can't go wrong with either. I opted for the Bushmaster, and I've been very happy with it so far. Conversely, I plan to build my next one off a RRA NM lower.
It also might help to know what is your intended use? Are we talking a plinker? If so, what ranges?