My personal though, about 1 and two position training:
One Position is good:
- When you have good trainees, who could stay in the top 2% of his age group because in young years you would get a lot money for those extra pops, who make the difference betwen average and awesome. Also this could help you to lineup a stronger formation in more important games, in the phase of the game, where your rookies are still your main weapon.
- When your team is so strong that rookies would be your weak spot(and buying great players who are still young is more expensiv then a more experienced player at those level who is 3 years older - so that he could participate in the 2 position training you make from time to time)
- When you start playing during the season to play BB, i recommend 1 position training, because it is even hard to get only 3 solid trainees with the money - after the next draft you could decide if you want to have more trainees^^
Two Position training:
- if you have 5/6 young(but don't start wasting training spot with fillers like in the one position training) and "average" trainees, 2 position training makes it easier to compete.
- If you don't like the "let them play" option, for 48 minutes game from your traineess. It isn't that bad if you sacrifice a training spot, for managing minutes.
I don't think that one of them is superior to the other, and done both during my career, even actually i make bg guy training for 2 position and small guy training for one position(i had to "very small" SF as main trainees).