After much deliberation, I chose the Edge Pro #4 because I didn't want the hassle of buying extra parts later. So far, I'm really impressed with the kit. I sharpened my Gyuto, which had a pretty notched edge, and although the process takes time, it's given me the best results of any sharpening system I’ve tried (and I’ve used whetstones, paper wheels, electric sharpeners, draw-through systems, and more).
It’s easy to use and highly accurate. I do wish I’d ordered the magnetic holder with the main kit, as it’s a huge help and really should be included in the premium set. The magnet eliminates the need to constantly hold the knife in place while sharpening with the stone. Maybe with more practice, I won't need it as much, but it’s a great tool for beginners.
I only wish I had bought this kit sooner instead of trying so many other options (and creating some "interesting" edges on my knives in the process!).