Thanks for the replies guys, I was also leaning more towards the AR-15 for the simple fact of how familiar I am with it. It also wouldn't be an issue to take it to work with me when we go to the range and throw some rounds through it. I'm not really worried about magazines, I have about 50 or so, along with a traditional bi-pod, a surefire flash light that has a fore grip that turns it on by squeezing the grip and a handful of other things.
How far can you typically shoot an AR-15? I can get 500 yards consistently with iron sights, but how much further can I shoot before I run into issues? I've never been to a range that has targets set up further then 500 yards.