You forgot one important diference. The video slot. Try a toaster/flyer in a 500 or 1200. What else does the Amiga still compete with the PC at?
Actually several of the Zorro expanders for the A1200 have an AGA inline video slot on them as well so in theory you should be able to run a Toaster 4000 no problem. I only say in theory cause I don't know anyone who's done it, but I do know that they are toaster 2000 compatible at least.
:-D