U21 sucks.
I bought 2 players, first on level 2 (the one that comes free) and second on level 4 (the "better" one) and they both sucked.
They both got cartilage tear and they were out for 5 days, and that was on normal training intensity.
Also they seem to develop slowly because they never crossed the 3 star quality.
And finally, they are too expensive. I can buy 2 five star (or more if i am patient ) players for that amount of tokens.