Having bought various 'off the shelf' autoparts inserts, my observation is that blade material, profile shape and length has a great deal to do with the performance of replacement inserts. I haven't had much luck with them. Streaking and chatter are pretty common. The OEM wiper inserts, however, available from Impex seem to be made of a soft, pliable material and have a longer blade profile than many aftermarket brands. They work quite well on my Golf. I've yet to find any other brand that works better. No streaks/chatter/skips, just smooth, quiet operation and last reasonably well. The longer profile seems to be able to allow full contact and switch directions without complaint despite variations in alignment between the arm/holder and the windshield itself. Just my $.02 but they work well for me. BTW, I am not a Rain-X fan.
P.S. We get LOTS of rain where I live...