I have a DPMS 24" stainless steel bull barrel free floated with flat top receiver for rock chuck hunting in eastern washington. Mines in 1:9 twist, which is just fine since I shoot 50 ~ 53 grain slugs. I use a 6-25x50mm scope so I needed a riser to mount the scope. Standard A2 stock. I didn't like the standard DPMS trigger setup and replaced it with a Chip McCormick drop-in. It is chambered in .223. Shoots well. However, I bought mine without bolt/bolt carrier group. This is an SAMSI .223 chamber and not a NATO 5.56. Most DPMS weapons are chambered in .223 and so marked! The easiest way to to tell is check the markings on the barrel and it will tell you. Normally, it will say who the manufacturer is, the chamber and the twist. On my DPMS 24" SS bull barrel, the following markings appear -> DPMS CAL. 223 1-9 <-
I also have a Bushmaster with MPI (magnetic particle inspected) 20" steel heavy fluted chrome-lined chamber and barrel 1:8 twist, 5.56 NATO chamber, which is my competition weapon (Service Rifle), with a Jewel two-stage adjustable trigger, KNS trigger/hammer pins and retainers. For long range (1000m) some people are using 1:7 and heavier slugs. I confine my self to 600m service matches and 500m for rock chuck. Barrels seem to last longer in 1:9 or 1:8 twist, instead of 1:7 twist of the GI M16/M4.
Either weapon will serve you well, for the purpose you state, both are reasonable quality AR class weapons. I have issues with all commercial (civilian) ARs in that bolts and bolt carriers aren't to the standard I care to see, which is why I build my own bolt/bolt carrier groups from mil-spec parts (which is an issue in washington, since you can not legally use a M16 bolt carrier in a civilian AR), which means that I have to deal with locating AR bolt carriers that have been magnetic particle inspected and properly marked and head spacing, but any gunsmith can check that out for you.
I've seen issues with staking on the bolt carrier and neither manufacturer goes through the trouble of magnetic particle inspection and marking of their bolts or bolt carriers.
One last comment, is good quality mags are a must. I use only Colt 20's for both hunting and competition, with Wolff springs.
Hope this helps.