Will I need a variable flow volume control for my new 2.5 GPM shower head? Or will it work OK to just use the on/off feature of a pressure balanced temperature mixer?

This will be going into a remodel with new piping. Right now I have a seperate hot and cold valves that mix at the divertor and then goes to a showerhead that could sink Noah's ark. But I am sure the permit inspector will make me install a 2.5 (or lower!) GPM head, as well as replace the valve with a temperature contolled one. It seems that the low flow head will need all the pressure it can get, in order to spray right, with enough "blast" pressure and water volume to rinse the soap off. I suspect that a volume control valve would be turned wide open most of the time. I also suspect that a useful volume control would need to have a pressure/flow characteristic that closely matches that of the head, in order to get a flow that changes evenly over the full rotation range of the valve.

Give me your thoughts and experiences of using just an on/off control. Is the spray sometimes too much like "stabbing needle" jets?
How do I go about choosing a valve with the appropriate pressure/flow curve? Valve spec sheets don't even touch that issue.