+1.
I can't think of any reason a tuner would want the power over speed instead of power vs. rpm. Every change in the tune you'd ever make, you do it at a certain rpm. So unless you want to back-convert to the rpm knowing your gearing numbers, the speed is pretty much useless as far as I'm concerned.
The only time that we really use the mph based graph is in some of the higher horse power stuff that climbs through the rpms very quickly. The mph based graph slows the ramp down and makes it a lot more pleasant to look at vs a vertical line
This is a dyno graph from some testing beginning of last year with my car and you can see how much more difficult it is to read vs the mph based graph posted above
(never mind how the ramp dies at the top of the rpm band. we were testing blower efficiency and we were spinning a V24 X trim well beyond its limitations hence the dramatic loss in hp up top)