I've been to all of the locations for character breakfasts some time in the past (although not necessarily with the current character cast). Here are my reasons for choosing GK.
I've always had excellent character interaction (B9erSteve, I don't know what happened with you!)
The character variety and number is good.
They have a large buffet offering good variety
Food quality is pretty darn good.
Longer hours
It's just a really fun place.
In comparison-
My experience at Storyteller's was good, but the number of characters wasn't as high and it just lacked the fun/Goofiness of GK.
Same for PP (Lilo and Stitch at PCH) as Storytellers'. The food variety was better suited for kids at GK.
The Plaza Inn is a bit too big with the indoor and outdoor seating. Consequently, the characters can take a long time to get to your table. This appears to be a problem if you do not get a really early seating, but I personally would rather be riding rides first thing. I think the food quality and variety is better elsewhere. It can be a really fun place though.
Another thought: I had a
AAA character breakfast coupon on a previous trip, and I was able to use it a noon at GK. I really like having a character meal at lunch time after spending the morning riding rides (before the parks get crowded). The food variety is great at noon and the characters seem to have more time to spend with you at lunch when the meals are little more leisurely.