Unless a large (more than 25) percentage of your work is higher than two stories, I don't see the point in using a pole longer than 18ft (3x2 mt). This will reach almost all two story windows, even over the average conservatory. For the odd higher job get a longer pole out of the van.
We have a variety of 3x2 m poles, but the lads prefer converted Unger telescopic poles. They are cheap (about £47 plus alloy end cone, plastic gooseneck and pole hose - total less than £65)
They are LIGHT - you can wave them about with one hand

The clamps are easy - twist action.
The inner locking cones last for about 3 months, but replacements are only £1.50 each.
Spend umpteen hundred pounds if you want - our poles do the job, they're almost indestructible and none of our lads have any shoulder/back problems.