Thunderpig,
Do not know that I agree that any group has an advantage over another in training. For starters, some of the express carriers had training programs specifically designed to replicate Delta's. Others had very tough, high wash out, programs due to the fact they desperately needed Captains and were upgrading people very early. The FAA and the Program Designees were very cautious and would rather hand out a pink slip than get debriefed post accident.
Don't know why, exactly, but when we went through the A-10 drivers are the guys who had a hard time in training. Mostly it was not making friends with the Flight Management Computer. Both went to SWA and things turned out fine for them.
The wake - up for the military guys is that the regional guys have already been through a very Delta like school 4 times (on average) and have flown a very Delta like profile for thousands and thousands of hours before they set foot in the door. In 2007 the first week (or so) of aircraft training was the FMC. In our group the regional guys had the entire week's work done by 10:00am the first day and were released while the instructors focused on the former military guys who were a feeling very below the power curve after seeing the rest of the class finish the task perfectly within 5 minutes of getting the assignment. (but realize the military guys were exactly where they were expected to be on schedule ... the others had been playing with the FMC for nearly a decade and were relying on training they walked in the door with and had been using for thousands of hours).
Other differences are the radios are run on line. Often you're getting a four instruction taxi clearance while slowing through 80 knots and performing an after landing checklist, talking to the Company about a gate change and coordinating with ramp. It is very easy to get distracted (and there's been times where a guy just has to say ... "let me get caught up over here" ... which beats pulling into the gate and seeing the Captains weather radar is still on, or the flaps are half down). I joke with my Captains that I'm placarded with a "four instruction limitation" ... more than that an a data dump is possible during a three minute taxi ....
I think everyone that shows up for training has the right stuff to be trainable. There are enormous differences in experience. Most regional pilots will be most challenged by just learning their way around the training center ... for them it is going to be like an airplane change... same stuff, different jet. For some military guys it is going to be a whole new way of flying airplanes and a new mission.
Delta knows this. They've trained thousands of pilots and it works.