- I don't know how much training said player will lose (due to fouling out...
Then you don't know if the player is really aggressive and the whole thread makes no sense. I mean, you won't know the exact number of course. But make an educated guess and work with that number.
- I don't know for sure how much 46 minutes a week instead of 48 minutes costs in training
There is a table with the results of an ancient study. Somebody will find it for you if you are interested.
- The price difference does not exists when it comes to drafting/buying players who just got drafted
Then go for the not aggressive player. You have all to win and nothing to lose. A no brainer. (Everybody agrees that the supposedly better defense don't compensate for the fouling outs)