Don't know about the edge but the Specs are great. The opening isn't really that big and the light covers it, but you can always put a piece of mesh over it if you want. The filter works great and you really only need to do a water change once a week to keep things clear. I'd definitely recommend the spec, either III or IV.
@kissthepilot, I like the Edge better for several reasons. First, the top is not open (my betta somehow managed to get out of the small gap around the light on the Spec and apparently died; never found him). Second, you can set the lights to either white or blue. However, the opening is very small and thus difficult to get your hand in to arrange things. If you go with the Spec, rig something on top to prevent escapes. Here's how I did it now that I replaced my poor little Kenny with a new betta (it's a plastic lunch meat tray):