The three biggest things that differentiate ARs are; Durability, Accuracy and Features. For example, ignoring brand for a moment, the basic ARs (like the ones you are looking at) will likely give you a few thousand rounds worth of durability, enough accuracy to go with iron sights, a red dot or a medium powered optic, and the features associated with a standard AR (dust cover, forward assist, easy to attach an optic, plastic handguards). If that's what you want, then pick your favorite company. I'd recommend Ruger and Del-ton over DPMS, as DPMS does have a long history of making out of spec parts. I'm not saying every DPMS is bad, but I have seen them and it is not hard to find examples online either. I think Ruger and Del-ton offer higher quality bolts as well, based on their material choices. They will certainly outlast the barrel.
Now, there are a few ways to spend a bit more and get a bit more. Plenty of people have mentioned Colt, so I'll start there. Colts offers much greater durability and you probably won't have to replace any major parts until 10k rounds (or you can shoot them until they break, it's your choice). Accuracy will be the same, iron sight/red dot/medium powered optic. Features will also be the same. So for $200-300 more, you are buying durability. Windham Weaponry also falls into this category.
People also mentioned PSA, which is my favorite brand. You will have to buy it online and have it shipped. With a PSA Premium or CHF upper, durability is going to be on par with Colt and accuracy will be as well. Where PSA stands out from Colt is that the features are endless in comparison. You can choose a mid-length upper, which is a big improvement over a carbine with no downside. You can choose a 14.5" or 20" barrel. You can have free-float and a low profile gas block. Plus it will cost less all said and done.
BCM will offer an upper that is similar to Colt and PSA, but a complete rifle or complete lower that is way over-priced. A lot of people have bought a BCM upper and paired it with a PSA lower, which is a smart and cost effective idea.
Hopefully I have added something to this conversation that is more objective than simply saying to buy brand X or Y. I'd recommend you get a PSA 16" mid-length barrel from either their Premium or CHF line, along with a lower. Get a FSB if you plan on shooting sights or a red dot, and a free-float if you plan on using an optic.