Just buy one. Its not that big of a difference. Everyone has their own opinions. Its not a big deal. Pick the one you like and enjoy it. Honestly, varmint hunting at 500 yards isn't something a .223 is going to be overly good at. Varmint bullets at that distance are going to be all over the place with any wind. Heavier bullets are going to fight the wind better, but they are going to have much more drop, making it that much more critical that the scope is of high quality and tracks true. Making hits on a man sized target is one thing. Hitting a groundhog's head is another. I think you continue to push the limits of what you want out of this rifle while continuing to look for bottom priced products. I understand this can be a big purchase, but go read up on AR15.com. There are hundreds of threads talking directly about what to expect out of different brands. It has all been covered there multiple times. You have multiple threads asking the same questions.
Here is what it comes down to. Some DPMS rifles shoot better than some RRA rifles. Some RRA rifles shoot better than DPMS rifles. RRA has a great reputation for accurate rifles. DPMS isn't a slouch but they don't quite have the same reputation. Pick what you want of the two. I can't tell you what to buy because I'm not you and it isn't my money. You have to buy what you want. Buying what I want may not make you happy.
I suggest before asking more questions here of which AR to buy that you go read up on AR15.com. They are dedicated to the AR platform over there. There are tons of reviews about how each brand performs and any issues that have popped up with any manufacturer. The info there is endless. Once you get a feel for what everything is capable of buy what you want. BUY WHAT YOU WANT. That is the key. Buy what floats YOUR boat.
