Why would Queen to f7 be prefered by the engine?

In my head I sacrificed the knight to e6 because it gave a check that would only be solvable by taking it by Bishop or Queen. 

My enemy took with his Bishop, I recaptured with mine keeping the attack on the Queen and Zugzwang my enemy to take my Bishop with his Queen which I would then again recapture with mine, making the game absolutely winning for me (atleast I thought so). My enemy proceeded to move his Queen away, giving me a checkmate (second screenshot). 

I don't get though why the enigne would prefer Queen to f7 like shown in the first screenshot. 

Thanks for any Info!

It does not matter. White wins anyway. There are no bonus points for a faster checkmate.