H2 BR by far. Then the BR then the DMR, though that largely depends on the map. If it has long sight lines ill probably go with the DMR, if not, ill stick with the BR. Besides, in WZ BR's have a REQ lvl of 3. You don't get access to the DMR till lvl 6.
Battle Rifle. I hate Reach's DMR. Halo 5's, on the other hand, its good. Just too easy to use, still has bloom and huge hitboxes. I like Halo 2, 3 and 5s BR. My personal favorite is..yes...Halo 3s. 2's is broken but still fun to use, and its RoF is a little too fast for my liking. Halo 5's was too easy to use for a time and had big hitboxes/high bullet magnetism. Now it's quite unpredictable with control, has spread that it doesn't need, has a better RoT and the same hitboxes and magnetism. Halo 3's has just a little too slow of a RoT but still handles great and feels fantastic to use, ten and a half years later. Yes it has spread, the servers were finicky, it has projectile physics that needed improvement (or hitscan used instead). That aside I still love the BR more, and Halo 3s the best. Reach's DMR has massive bloom that destroyed the game's pace and gameplay flow. I don't like its visual design as much as Halo 5s - 5's is so nice. I used to hate that part about it. Then you have its absurdly slow melee animation. On the side, Halo 5 DMR > Reach DMR
To me, the BR is for short to mid range, and the DMR is mid to long range. They both have their uses, depending on the situation. For me it is comparing apples to apples, you have a granny smith, then you have the red delicious, both are good but different.
I'm definitely a DMR guy myself, I think its way more useful at longer ranges, like outside of red reticle range. BR is pretty much useless out side of red reticle range, so in the absense of sniper I just stick with DMR