Recommended Battery For 3dr X4

Can anyone tell me what the recommended battery for the x4 is? I tried the stock iris 3s battery, but it seemed to need a lot of throttle input at hover. Was thinking a 4s battery would be battery? Thank you.

For the 2013 version, a 3 cell 4000mAh battery is recommended
and for the 2014 with the black 880kV motors, a 4 cell 6000mAh