I prefer to train via friendlies, due to the fact that you can keep track of exactly how much energy each player has and make as many subs as needed to take players off if needs be.

The other benefit is the packs and cash that is generated from these games. Granted cash becomes pointless later on, but the packs are useful in being able to power train or keep the team fit when you get given two games in a short period of time.

I only ever play friendlies after my days competitive games are over however - and I always make sure that if I am playing them the next game is not in the early hours of the next day. I very rarely use normal training methods, unless I am power training a player, or I simply don't have the time to sit and watch/sub through a game.