For me I can see how the slx will save possibly an hour on a long day. The fact that when your doing upstairs windows it's as easy as doing downstairs because there is no flex is amazing, that on it's own can speed you up no end.
I think the harris pole is fantastic for the price, I have one for trad stuff and it's brill possibly better than an xtel, but the slx is in a different league. The price is comparatively high but if you could even save only 1/2 hour a day, the pole would have paid for itself with in the month, presuming you have the work.
Simon.