If you're talking about the quality of their chips, I have no idea. Since I never work with AVR.
But I you want to know which line are easy to learn, then my vote will go to PIC.
When I was going to start my micro-controller journal, yes I came accross the same question as you're now. Here is what I found.
1) Free sample can be obtained from Microchip by using thier online service, but I never get one from atmel. I tried thier online form and calling their local sales representative. All application look like droping a stone into sea.
2) Microchip application notes are, in my humble opinion, far better than Atmel one.
3) Online forums, Microchip one forum.microchip.com, and PIClist www.piclist.com are awesome. Even though I know one of Atmel.
Go for the pic's,easy to learn and very user friendly.I recently started,3 month's ago,and I have learned a lot. Start with flowcode from Miltimediamatrix if possible.