Yes they do train faster, but keep in mind, that they are also less experienced. Personally I try to keep 2 or 3 in my selection, and sell them after a couple of seasons. Their worth increases also as they improve. Ive had quite a few youth players by now, and some really excelled, ended up earning their place in starting line up, playing in the league and cup aswell. Eventually selling them to make space for new youth...and sell them at a good age in comparison to Nordgens. I think I even have a couple of regular buying managers at this moment.

Anyways, I'd say its worth it if you can miss the tokens and are looking to evolve the player and cashin money later. In comparision to buying though you wont end up in a bidding war and potentially lose all the tokens put in.