FK: Depends on a lot of things, but here are a couple to consider:
Seniority makes a huge difference here. Night and day, literally.
So although it might be tempting to take the first widebody slot, it will likely mean more hub turns. Newsflash though, hub turns is what we do (mostly).
If offered a widebody in training I would probably take it. If not, I would stay in the back for a year or so, and then bid to the right seat of the Boeing. The reason is that there will be more people behind you sooner in the Boeing than in the widebody (most likely anyway). The sooner you can get those folks behind you the sooner you get off reserve and into a custom line, and eventually into a decent regular line. Even if we hire directly into widebodies the chances are better that more newhires will go to the back or right seat of the Boeing and thus you will move up quicker in the Boeing. I'd move to the right seat of the Boeing just about as fast as possible while hiring is moving like it is now.
If you don't mind the turns and need the money, or want to go international, go for the MD-11 or the Bus and don't look back. If you don't mind domestic flying and can stand the winters in Grand Forks, go to the right seat of the Boeing for a while and let the newhire (or me) do the walkarounds in the blowing snow and enjoy some seniority. After a few months you'll have plenty of ideas about what type of flying you prefer here, and then you can bid accordingly.
I've heard that the widebody side is a whole other airline and was encouraged by my sponsors to move out as fast as possible. After 2 years on reserve in the back of the Boeing (no hiring) I was happy to just get a line once in a while, and thus decided to stay in the back to enjoy the afternoon out and back trips that I could hold. Now I could almost get the same trips in the right seat of the Boeing, so it is certainly time to move up.
My personal choice is the right seat of the Bus though, since to me it would be worth the money to spend some time back on reserve. Don't want to sit sideways for too long or you might forget how to fly!?!
Everybody is different and it is really nice to have options.
Looking forward to seeing you on the line.
FJ