Last year my opinion was Diara should have redshirted because we had so many bigs on the roster and there weren't enough minutes to go around. This year I would guess both of these guys could redshirt with the options we have from 2-4. Gilliam is very young so a redshirt year could be very good for him. It doesn't seem like Hardnett is quite ready to contribute in a significant way.
I hope both of them are beyond expectation and can play right away. I think we need accurate perimeter shooters more than anything to stretch the D so I'm not sure either of them would fit that mold.
We can also use some interior scoring too. Sounds like Gilliam is probably closer to 6'5" and might find it hard to score down low until he gets his moves polished against bigger players. I don't think Hardnett is a back to the basket guy.