I figured I would throw my 2 pennies on this one.
I own the Sharpmaker, the Edge Pro, and the Wicked Edge.
All 3 work great. Sharpening has a learning curve. Each of these systems has a learning curve. We all learn differently. We all have different abilities physically (related to muscle memory and ability to hold things steady). We all will use these systems differently, looking for different results.
The Edge Pro is great, but I have had knives that I have ruined on it (cheapies), because I couldnt keep the blade steady or get consistent seating. Recognizing my limitations and using the right system for me, is the trick on a particular knife. I have never had this on the Wicked Edge, however I have had issues with the flexible knives on the Wicked Edge. Bottom line is, I think both systems can do any knife, but your sharpening knowledge, dexterity and muscle memory, physical ability to not have heavy gorilla hands, your experience with each system, your needs, how much time you have, etc all come into play. I learned 50% of the Edge Pro fast, but hit a HARD wall on certain knives. I got to 90% proficiency with the Wicked Edge in a month, but soon learned although it can do FFG, I prefer the Edge Pro for FFG (when I say FFG, I dont mean chef's knives, I mean thick FFG knives). This is because of the clamping consistency is brainless on the Edge Pro, but on the Wicked Edge you need to confirm the centering of the blade with an angle cube. It is easy to do and quick, but again, personal preference. Another example, I prefer to do tanto's on the EP for now, until I get used to not rounding the corner on the Wicked Edge, so I just need more practice.
If you LOVE to sharpen knives and tinker, and do not mind investing time in each knife, then EP or WE will be awesome. If you are looking for fast, utility edge sharpening that takes minutes, then go with another option. I like doing all sorts of sharpening for different purposes. I own the EP, WE, and Sharpmaker, like I said, and my next venture will be belt sanding and paper wheels, just to round out my skills, so I can offer my small customer base more options.