Guys, think about it. If you have to square a work piece, do you really want to gnaw away at it with an end mill like PacMan? Why do that when you can cut out to a 6" wide swath in one go and produce a much nicer surface finish that is as accurate as your tram? The Superfly will repay its cost in end mills, time and aggravation, trust me. On the other hand, if you often work with smaller work pieces or need to cut a ledge then the Sherline, being essentially a single insert face mill that costs all of $73.00, is a very good tool to own.
Personally, I think you should have both flycutters. Come on, you know you want them ...