We were just at POP for 6 nights over 2 seperate weekends earlier in the month (in between DVC stays) and I really liked it much more than I thought I would. I have never stayed at the All-Stars, or POR for that matter, so I can't compare it to those.
Both of my kids 7 and 2 loved POP with all it's big oversized icons and colorful surroundings. We almost went with a moderate but my 7 year old son really wanted POP after looking at the Disney website, so we planned on trying POP for 3 nights and then somewhere else for the 2nd weekend. After our first three nights at POP I cancelled our other arrangements after securing another 3 nights at POP, that's how much we enjoyed it. Good luck on your decision.