your talking chevy, this is the ford group
pic's and avr's are two competing projects, and in all realistic manner does the same thing (not counting that microchip, the maker of PIC micro-controllers have some of the worst development software this side of TI, but they are stupid cheap)
arduino is a noobie oriented set of libraries, IDE and form-factor based on AVR chips at its core, there are attempts to bridge some gaps but all in all why use a 8 pin PIC and then choose an AVR development system to try and mutilate, just choose a 8 pin AVR (or whatever) unless your buying millions of the things your talking about spending less than 10 bucks for the BIGGEST avr, or PIC
choose what you want to work with
if you have a PIC(which if its scavenged means its probably non programmable) then you need to find a pic system