There has bee na lot of threads on this. I'll summarise from what I've picked up here and experienced for myself.
Freehand
A lot of people swear by it and wouldn't use any other method. Downside is that it requires a lot of practice and skill to achieve excellent results.
Sharpmaker
Excellent sharpening system. Handles not only knives but scissors, fishhooks and a whole range of assorted sharp things. Very easy for beginners to achieve very good results. Main downside is that you can only sharpen at two angles, 30 or 40. Not the best system for reprofiling.
Edgepro
Probably the best out there for knives. Many angles and great for reprofiling as well as regular upkeep. Main downside is cost.
Lansky
Works OK but very fiddly and annoying to use, particularly on larger knives.
If $100 is your ballpark then I'd go the Sharpmaker unless you want to learn the skills required for freehand.