Same for me, I have tennis elbow issues.
Xtreme brushes 90% of the time, with Extreme pole and I use an additional 30m of Gardiners Reinforced Pole Hose on my main reel (to keep it lighter and more manageable).
I use the Xtreme stiff, all day long.
First cleans, no problem, with an Xtreme stiff brush, No Nonsense Degreaser, plus, a cut down brush (shorter bristles and shorter width, acts like a large toothbrush) plus a 'magic eraser pad' that I have attached to a Gardiners quick lock, using tough elastic bands. A few little tools I made myself, just in case I need them.
I also have an Ultimate medium (I bought it just to try, good brush, but I keep reverting back to the Xtreme stiff) and a Supreme flocked. The Supreme flocked is about the best brush for leaded windows in my opinion, but for me, it's a tad heavy.
I found an original Xtreme flocked brush in my garage (unused). I now use this(with red fan jets) for fsg cleans, as again, I need light brushes.
I recently purchased the new Xtreme TaperTec brush.
Initially, I was disappointed as it doesn't look up to much!
However, it has a very good scrubbing action. I think an extended width version of this would be very good on commercial glass.
So for me:
Xtreme stiff for house bashing and Xtreme TaperTec for bungalows with large panes.
Looking forward to the new Xtreme Sill Brush (but kind of underwhelmed too, now!)