First of all, I think when you get to fly a Widow NG, you will really be surprised, and many very experienced fliers that have flown the Widow maker and the Widow NG have been surprised on how well the Widow NG flies, especially factoring in the cost.
Now on the Zephyr, I have read post after post after post, that clearly state that the Zephyr is not an SUL or even a UL, it is a light standard, period. Haven't read one post yet, that raved about it's low wind performance. The difference, for me, between flying the Zephyr and flying the Freestylist UL, is like the difference in driving a Corvette compared to a Lincoln Navigator. The Zephyr feels heavy flying, and it also feels heavy just carrying it in the bag. Not sure what it weighs, because it seems that Prism doesn't want that shown on their website, but I'm betting it weighs alot more than other low wind kites. . The other issue with the Zephyr is the trailing edge flutter which acts like a speed brake any time the wind picks up, which I think is part of the problem. As soon as the kite achieves some decent speed, the TE starts buzzing, and the kite slows down. No, I haven't set the leech line, because of the reported problems with trailing edge wear, and the leech line ripping through the TE if the leech line is used. I have asked on the Prism facebook page about using the leech line, and received no response at all from anyone, users, or the company.
I have read quite a few posts from people in the UK, where if you claim a product can do something , and it can't, you can get into legal trouble. They are all surprised that Prism hasn't been called out on their 1-17MPH claim, which is obviously not true.
I tension the leech line on my zephyr, and do not have any noise or braking from the trailing edge. I have not seen any wear on my trailing edge.