If you go to the archives and perform a search for "edge pro sharpening", you will find an immense amount of posts. I just went through that exercise and I think you would be amazed at all the information.
I do not have any experience with the Sharpmaker, and I am just starting with the Edge Pro. I used a Lansky prior to trading up to the EP.
If you go the Edge Pro route you will most likely buy it directly from Ben Dale, so there is no means of finding it cheaper (unless you find a used one).
I have a sharpmaker, EdgoPro Apex and Professional and let me tell you - there is no comparison. With the 204 you have a choice of two grits and two angles. The EdgePro series gives you 6 grits and any angle from 10 to 30 degrees - up to 180 on the Professional with the scissor attachmenet.
Metal removal? I've used my EdgePros is reprofile my Busse knives - no problems at all.
Sharp? My knives will do all the sharp tests - push cut cigarette paper, slice a free falling sheet of paper, cut a coke can in half. Yeah, they're sharp.
Cost? The cost of an Apex is about the same as the cost of a decent knife. A totally worthwhile investment.