I have used the xtreme for 6 months. Nice and light, but I was going over the glass more thinking it wasnt doing as much. Not saying it wasn't, just felt like it.
I now use the supreme range. At 200g, sometimes can be a tad heavy. Ok doing up and down windows, but sideways it pull son my arms.
Havnt tried the ultimate medium yet. At 180g its a little lighter also. Not sure about shorter bristles though.
Note, I always rinse on the glass. Way less strain