I know one of the things that seems to impress the hiring types is people who have trained successfully on multiple aircraft. I overheard a conversation to this effect between two members of the interview panel when I was interviewing. The rational was basically that if you've gone through multiple aircraft schools successfully, you've shown your "trainability," and are more likely to do well in training at Delta.

So it would seem this decision is a wise one - and probably what they are looking for.