I find that it's most important to mate sharpener with personal preferences.
Using a stone takes experience, but can be cheap and fast when you get it down. Until that point, it can be frustrating to many, I imagine.
The Spyderco Sharpmaker is inbetween free hand sharpening on a stone and using a system like the Wicked Edge/Edge Pro. It's quick, painless, and gets great results (plus it does teach a bit of the technique needed for sharpening on a stone). It's limitations are reprofiling edges and the quality of the edge depends on how straight you keep the knife during sharpening. I recommend the Ultra Fine and Diamond rods, but they add a LOT to the cost.
The Wicked Edge/Edge Pro systems are expensive, but after a few trial runs pretty much anyone can get a knife super sharp. It costs as much as a high end production or moderate priced custom knife, though. Never having used one, I can imagine the setup/storage of such systems would take longer than alternatives. I would mostly recommend this type of system when using ridiculously hard to sharpen steels.