You ever hear of anyone breaking an AK bolt.....nuff said.I like the fixed ejector too,you'll never have to worry about the ejector spring getting weak and needing replaced or crap building up in/around the plunger and clogging it up,you never have to worry about the heat from the impingement system cooking the bolt,firing pin spring,ejector spring,or cleaning all the crap with a scraper off of and in between all those "little"lugs on an AR bolt......The gun runs so much cooler than an AR that you can touch the bolt after firing several magazines,try that with an AR.
Not sure how often you will have to do that,but it proves how much cooler it runs,which means less wear and tear or fatigue on important parts,not to mention when all that gunk is deposited there in an AR you need to keep the gun "wet" to run,which can pick up junk floating in the air(aka that talcum powder-like sand in Iraq) and make those already tight tolerances closer,meaning more crap in the action causes the gun to barf.
Did I mention easier to clean...why? Because it vents the burnt propellent outside not onto or into the chamber and all over aforementioned important parts,OOOOHHH and because it doesn't send that HOT dirty propellent gas where it feeds,the carbon that does get into the chamber area wipes off because it's not cooked onto those important parts.
The gas piston driven operating system is a time proven design used in many of the most well know-to-be reliable battle/assault rifles of the modern era.(do I really need to cite examples?)I'm not saying impingement is a terrible idea,but the way Stoner's design works,the gun shits where it eats,in my humble opinion that's just a bad idea no matter how you look at it.Say what you will about how far the AR/M16/Stoner family has come,I ask you this,if it's so damn great why didn't good ole' Eugene use it again.Also why in the hell does everyone who thinks the AR is the holy grail,say that "sure it's reliable as long as you maintain it? Ok I'm not advocating never to clean your weapon,but ummmm when have you EVER hard that statement made about an AK?
Ergo's: Ok sure how you hold it,how you find your cheek weld and all that stuff is subjective to the end user.I will say this,I firmly believe that if you put an AR and an XCR side by side on a table and let some Joe smo who has never handled either one before pick them up and ask them to figure out how to run it,the XCR would win.This of course is pure conjecture,but in my mildly humble

opinion I think the XCR is more INSTINCTIVE more natural.Again purely my opinion.
I don't mean the AR is awefull or it's a huge difference,but I do believe there IS a difference,which to an experienced operator could mean those few milliseconds between you sending Hadji to meet his 77 virgins,or your wife and kids getting a really shitty visit from some gentleman in uniform.Simple equals speed,speed equals survival.Remember it's not who fires first it's who hits(well) first that usually wins.
The ability to use a folding stock,if you have the want or need to do so,because there is no need for a buffer or spring in the stock.I'm surprised when people who have been looking into the XCR don't know that.Folding stocks for some are either love or hate,but you cannot deny the convenience of making the weapon more compact if your profession or needs call for it.The left side charging handle allows(right handers)to maintain a firing grip end eyes on target while doing a mag swap or malfunction clearance.With the AR you have to lower the weapon to clear a malfunction and/or chamber a fresh round.
Someone mentioned the interchangeable barrel,great point again.There is no need to change uppers to change calibers like with an AR.The bolt is easily removed from the carrier.The magazine well in the XCR positions the magazine higher in the weapon vs the AR so no need for a feed ramp as the cartridge is already pointing down the tube when the bolt strips it from the magazine.The benefits are more reliable feeding because the feeding geometry of the cartridge has less angle to overcome to be chambered.
The upper is a complete unit with fully machined accessory rails full length on top and I believe about 12" inches long on the 3,6,and 9 O'clock positions.Which means that the barrel is free floated to enhance accuracy.All this for roughly 500 scabs below the price of the Colt M4,Hey that'll buy a caliber conversion kit or a case of ammo or two.I know I'll get hammered for this one but most of my rantings are fact,my intentions were not to flame the AR,but to highlight the differences between the two systems.
I'll end with one last thing,that I'm sure we all will agree on.The XCR has a great customer support base,Terra kicks ass and she devotes alot of her free(read unpaid)time because she truly cares,why the hell else would anyone do that? Allison is also great to work with,and they both give a damn about what they do.