Well, both have some issue. Dimitrov wants to imitate Federer and fails in almost every way. If he had his own style of play and played with it then he would've been better than he is now imo.
On the other hand, Tomic has a huge confidence. He thinks he can do anything and can be the best player of all time. He expressed the latter thing publicly which was not good. Having confidence doesn't do anything good without having the capability of using it.
Comparing their current condition to other great players at their age, neither of them has the capability to win a slam, let alone more than one. But they still have time to improve their games and be good players. We need good young players right now. We'll see what they'll do. We just have to wait.
Nirjhor, not sure when people saying that Dimitrov is a baby Fed is fair to him. I don't think he is actually imitating Roger per se. Nobody can 'imitate' Roger. Fed is a tennis genius, no question about it. well, Gasquet was a new Fed back in 2005/06 (I wish, because I like Richie so much) ... he got nowhere