Histogram inputs to kstest2 function

If I created two histograms and wanted to know if there was a significant difference between them using the kstest2 function what would be the input:

h1 = histfit(v1 , 10) ; h2 = histfit(v2 , 10) ;

x1 = h1(1).Xdata ; x2 = h2(1).Xdata ;

y1 = h1(1).Ydata ; y2 = h2(1).Ydata ;

Is the input into the function

[h,p,k] = kstest2(x1,x2,'tail','larger') OR [h,p,k] = kstest2(y1,y2,'tail','larger').

Or do both work and the answer is just different if y is the input then that would describe if the frequency is becoming larger or if it is x then the unit of the vector, say days, is becoming larger. Can someone confirm that this is right.