For me, the characters at Plaza Inn are hit or miss. In 5 visits over the last 3 years, I've had 2 great with plenty of characters, 1 with about 5 characters (same as you see at the other locations) and 2 with only 2 characters in 90 mins, despite asking the handlers for help.
To me, Plaza Inn has the lowest quality food, and it is "self service."
Storyteller's, you will see 5-6 characters, but they aren't all the top characters. We did Storytellers this week. We had Chip, Dale, Pluto, Koda, Kenai, and Brer Fox. But the food was awesome. And you had servers to refill drinks, clear plates, bring fresh utensils, and assist with needs.
Our preferences is usually Surfs Up with Mickey. Food is good, buffet is kid friendly, yet has plenty of items for adults, you get Mickey, Minnie, Pluto, Goofy, Daisy, and STitch. Sometimes Goofy shows up too. The servers are great and friendly.
Goofy's is fun, and has a great selection of food. You will get Goofy's and 4 additional characters. The servers do a great job. The place is huge, so you may not be close to the action.
For us, if it is mainly adults, we do Storytellers, add in a few kids, we do Surfs Up, or maybe Goofy's? If my granddaughter asks specifically for it, we will still do Minnie's, but it is my last choice.