Biggest diffirence between pic and avr is the instruction set. Avr's have more instructions wich make assembler a bit harder to learn (more to know), on the other side, avr's are much better to program in a high level language (C for example). their more advanced instruction set makes it easyer for a compiler to generate efficient code - compared to PIC16 devices. The newer Pic18 devices have a enhanced instruction set of their own, including hardware multiplier, their C support had become good also.
Also, the complete development enviroment you need is diffirent for the two. you've got a programmer, software, etc... for a pic, but you can't use it for a avr, and vice versa.
It mostly comes down to personal preference. Try to experiment with both, and you will see what you like most.
As for the 8085. I don't see a reason to use it. All the info i find about it seems to point out it runs at 3Mhz max, and you need a whole bunch of external components wich make board production harder.
It might have it's advantages though, i'm not really familiar with intel's chips