Capt Bloggs and 411a,
Sorry, you are both incorrect.
Bloggs- think about the senerio above- the aircraft that has a STILL AIR Vx of 60 kts will climb MORE STEEPLY wrt the ground at 50 kts in a 50 kt headwind.
Vx is max excess thrust- IN STILL AIR.
reference:-
Performance of light aircraft - Google Books