I do all my work on waterstones since they give the best control over your edge. I've got some pretty expensive knives for work, so I want them to be shaped to the exact edge profile I need for the tasks I use them for. Most powered options are a too aggressive for these types of knives.
That said, a good buddy of mine has a Ken Onion Work Sharp. I think for beater knives and pocket knives, it's a pretty damn good option. It's efficient enough, plenty quick, and the edge you get off of one is great for a pocket knife. It definitely can give you an overly convex edge profile depending on how you use it, but if you use light pressure and multiple passes, you get a pretty flat grind and don't build up much heat.
Anything powered (and not wet) can potentially ruin your heat treat, though. Not to mention how much material they can remove in pretty short order.
That said, a good buddy of mine has a Ken Onion Work Sharp. I think for beater knives and pocket knives, it's a pretty damn good option. It's efficient enough, plenty quick, and the edge you get off of one is great for a pocket knife. It definitely can give you an overly convex edge profile depending on how you use it, but if you use light pressure and multiple passes, you get a pretty flat grind and don't build up much heat.
Anything powered (and not wet) can potentially ruin your heat treat, though. Not to mention how much material they can remove in pretty short order.