I have both AR's and Sig 556's, they are pretty similar in that they are semi-auto 223's and use the same magazines. IMHO both have advantages and disadvantages.
As mentioned earlier the AR-15 on account of it being available and popular for 40years or so has ton's of aftermarket parts and variations available. If you like 1911's and Ruger 10/22's because you can customize them the AR is for you. AR's can be tuned into extremely accurate rifles for target shooting and/or Varmint hunting.
The disadvantage to an AR compares to a PC and Mac thing, like a PC an AR has lots of parts available for it the problem is that the quality of those parts can vary quite a bit. There are lots of AR's that are shoddily built, slapped together and are likely to break the first time you run them hard. They need to be run wet with lube to run properly.
I think if you will read around a good bit about AR-15's you'll find that they are kinda 3 tiers of AR's made: 1. cheap ones built to sell on price 2. Mid-tier guns that are better made but still not full mil spec 3. Higher end Mil-spec guns that use better parts inside and don't break as often.
As for as Sig 556's go, I haven't had a single malfunction with any of the three I own. In general I think they are a more reliable firearm than an AR, even than the higher grade AR-15's. Sig bolts for example are rated to last twice as long as AR-15 bolts. If reliability is your primary goal I'd lean to a Sig 556 - but toss the mags that come with it and use good ones like Magpuls, H&K or Milsurp mags.
As to accuracy my Sigs have been 1-2 MOA guns whereas some of my AR's a 1/2 to 1 MOA guns, AR's in my experience have been a little more accurate.
There aren't yet as many options for customization of SIG's but more options are coming out. The rifles haven't been out for near as long as AR's but they are becomming popular so more stuff is being made for them.
So my summary would be that AR's are more versatile and SIG's are more reliable. Choose accordingly.
BTW in OKC Outdoor America had good prices on the Sig's. They were several hundred less than H&H. I bought a 556 Swat at OA for $500 less than H&H had them (sorry it was the last one at time). If you decide on a 556 Classic I'd wait till Outdoor America had them for $1350 or so instead of paying $1899 or more at H&H......................................DJ
