It is my undressed opinion that 8051 would be easier to learn than the PIC. The skip style instruction set can be a real pain to get used to for new comers I have found. Since, as I understand it, the AVR is similar I would vote again for the 8051.

Arif:
I think you really did come to the right place. Here you can learn practically everything there is to know about what is most possibly the nicest microprocessor to work with ---> the 8051 / 8052.
Michael Karas