Did you look here
http://www.us.kohler.com/us/Showering-Showerheads,-Handshowers-&-Bodysprays/category/431345/430957.htm#id=filters&color-filter=101783_BGD

I would go to somewhere like a Ferguson Enterprises and ask for information. Most of their showrooms have working displays and you can see the differences. I think (not positive) that all of the shower heads have restrictors in them to cut down on water use. You can have those removed - sometimes it makes a difference, sometimes not.