If there is forward momentum it needs to be overcome, which takes time.
Even if there is a forward momentum, you'll still be able to apply right bank, add max power and left pedal.
With the forward escape, you have only the vector from the main rotor. With the sideway escape, you have additionally the tail rotor thrust.
Therefore your escape out of the VRS is faster, and faster means less height loss.
And am talking about a real vortex, in which a solely increase in power only will increase the ROD...