I have two DPMS 308s, along with two stripped lowers. Here's why I went that way:
1. Better mags, with more variety. I really like the PMags
2. More vendors supporting the platform. I can get a wider range of uppers and components, for my lowers
3. Calibers beyond .308
Actually, I'm not the biggest DPMS fan, but their AR-10s aren't bad. Mine shoot well and are reliable. My R-25 (Remington-branded .308) doesn't like a few types of ammo, but will work reliably with good stuff. And my Sportical is less picky. But those are basic rifles, I went with DPMS because I plan on branching out into some of the other vendors. And, I do like knowing that I can add a .243, Creedmor, 7mm-08, etc. to the mix. If you don't like DPMS, there are a wide range of other vendors to choose from.
Honestly, I think either platform is fine. I just went DPMS, and now I'm staying with it. I have about 30-40 mags, and I like being able to swap stuffs across my herd.