I guess I just don't understand the Colt worship. I carried a Colt A2 in the Marine Corps, great rifle and no problems stand out in my mind after thousands of rounds down range in some pretty tough conditions. I now have a Stag model 3L that I'm just as mean to. I haven't put many thousands of rounds through it yet but I'm well past 1K problem free.
I just don't see a big difference. Maybe somebody can enlighten me with some actual facts?
I considered the model 8, looks way nice to me but I opted to stick with DI as it never caused a problem before.
No doubt a Stag will serve most folks very well. Problems arise when you run the rifle hard and long but unfortunately the information (it sounds like you want) is hard to come by. Sometimes you have to trust the opinion of those who see lots of use in AR style rifles. The first user that comes to mind is our military and they demand certain specs. Of course their major suppliers of complete rifles are Colt and FN. Not Stag. And as bigghoss pointed out "... professional instructors and guys who shoot competition they see a higher failure rate with Stag/RRA/bushmaster and the like as opposed to Colt/Daniel Defense/LMT and those when the rifles get lots of rounds through them in a short span repeatedly over a long time..."
As far as piston vs. DI in the AR, DI performs well in most cases. As the barrel gets shorter than 14.5" or in suppressed applications there can be advantages to the piston gun. The main advantage of piston in these applications is the gas regulator which can lessen the abuse to bolt components common in shorter barrels. If you have 14.5" and longer, the disadvantages of the piston become more noticeable, especially the heavy muzzle weight.