I believe Microchip bought Atmega.
You skill in the art clearly exceeds my own. I am unfamiliar with several of the processors you mentioned. I build a lot of radio remote stuff and various small control stuff like time clocks.
Microchip did purchase Atmel. I'm sure that is why so many of the AVRs are no longer available. The idea was to kill the competition.
PICs are an interesting breed. Its a pug-ugly instruction set; however, it seems to be shockingly efficient. Programs are always very small when compared to the same application on another processor. They are also very rugged and dirt cheap.