The water fed poles are streak free as long as you make sure to clean the frames well on your initial pass. Otherwise, the frames, which are dirty, will cause dirty water to drip onto windows. WFPs are ideal for buildings that are all glass.
I think the main benefit of using a WFP over traditional methods is how well the frames come out. It's faster to pole traditionally or ladder if you're not trying to clean the frames, but for a better, and more efficient overall job, WFP is better for higher windows.
Some jobs you're better off to do with WFP, but others traditional is more logical, so you need to quickly evaluate each job and decide which method will work best.