Only the 4 star player is ever worth keeping, unless you fancy hard training the 2 star - they do train fast, good to train up for the next season. The 4 star will cost you 24T just about half a scout. What you do get is the youth side, and again, they do usually train better than your other players. My young DL/DC gets 3 skill points regular, he's leveled up already, just got him other day