Best is completely subjective:
Are you sure you want breakfast? Lunch, dinner and the ice cream social are other options.
Which characters are you interested in - the big ones are Princesses, Pooh, and the classic characters (Mickey, Goofy, Minnie, etc).?
Where will this fit in your schedule? A lot of people like Chef Mickey's for dinner on arrival day, or breakfast at the closest resort on the day they leave. Others like to take a mid day break in the MK for Crystal Palace.
Is serving style important to you? Most are buffets, some are plated, others family style. Buffets give you greater variety, but you'll need to get your own food. We prefer to have ours brought to us.
Our tradition is the Ohana breakfast (though I'm considering Cape May next trip). It isn't Disney unless we have our picture taken with Mickey (Cape May has Minnie, but not Mickey), its served family style, and we have the flexibility of not requiring park admission - so we can do it on the day we leave.