I'm afraid they would Screwtype, perhaps in your haste to quit playing the game, you failed to notice that retrained units retain their experience.

As for the question at hand... The one turn, multi-unit retraining is MUCH superior to MTW in my opinion. I am still annoyed at the fact that one can only build one unit per turn per province. The way I would have designed the game would have been to implement a limit to the number of men able to be taken from a province for military service per turn, and b) increase the manpower costs for the units themselves. But hey, they didn't ask me...