I do wfp tops as I won't use ladders any more (hurt my back a couple of years ago, not going through that again), not happy with results but hopefully it's because I've only just started and am slow.
Trad the bottoms, far more comfortable with trad and feel that I'm quicker and probably not used to the pole but it's knackering my hands, arms, elbows, shoulders already! And I use an SLX with Xtreme brush - maybe I'm just not built to be a windie!
Assume you're doing domestic 2 storey places?
If you're aching poling that with SLX, I wonder if you're stressing a bit?
It could tense your body up.
It's easy to say and harder to do but, try to relax a little.
It may just help the aches.
Maybe just do your own windows and experiment on hand positions, shoulders, neck, distance from glass etc.
If it is that, once you relax, you'll be able to pole top & bottom.
That'll be quicker overall.