We have stayed at all three levels. The Value's are great, fun, and really neat hotels. However, they have a motel feel. The mods on the other hands, I really do think you step up to a "resort" feel, at least for us. Instead of being "kitschy" and ostentatious, they are instead relaxed, more "pretty", and more inviting.
We still find time to stay at all three levels, with the Deluxes our favorite, but you can't go wrong with Port Orleans Riverside, or any other mod. If you have the bucks, go for it, but by no means scrimp on any other part of your trip to stay at the mod.
Have a great trip!