FWIW, I have three different A-2s, all from the "current" batch issued for the USAF.
The Cooper A-2 (mfd circa 1988) is the most close to "authentic" -- it is based on a late 1930s jacket (I don't know which manufacturer, unfortunately) that was pulled out of the NMUSAF. Unfortunately, as was mentioned, the cut is designed for a pilot sitting with his arms down and wearing a Mae West -- if you raise your arms above shoulder level, the rest of the jacket will pull up to your chest!
My current-issue USAF A-2 is an Avirex (made circa 1999). It is modified quite a bunch from the "stock" pattern;
- Under-armpit extensions
- Collar hook deleted
- Side-entry pockets (hidden quite well, but still not stock)
- inside pocket and pen-pockets
In addition, the neck is noticeably larger than the original pattern, and the torso is larger than the original. In other words, in an "original" A-2, if I get one that fits me across the shoulders it is snug around my chest and abdomen. In the "current issue" Avirex A-2, there is plenty of slack (which I don't like).
Both of them are very, very tough. I treated the Cooper pretty well before I got into the USAF -- it had about 5 years of wear and the frequently-replaced areas (knit cuffs, etc) have held up reasonably well. The leather looks good and all the stitching is in good shape, too.
The Avirex I have deliberately mistreated! Since it was an issue item and didn't cost me a cent, I decided that I was going to try and get it to take on a weathered, beat-up look. So, for the last nearly 10 years I have worn it out in the weather, left it wrinkled up in my car in the searing heat, tossed it on the floor with my dirty laundry, etc.
I am disappointed to say that it does not look weathered. In fact, it still looks really, really good. I bet if I took it to a cleaner and had it cleaned, it would look brand new. The liner, the knit cuffs, the stitching, etc, are all still in great condition.
So, I definitely recommend both the Cooper (if you're interested in pure historical authenticity) or the Avirex (if you're looking for modern enhancements that make it more comfortable to wear). Avirex is called "Cockpit USA" now, BTW.