EPCOT without a doubt because it is so much bigger with more choices! I have only been to the California one once but to Epcot's several times. I think California Adventure only had maybe a dozen kiosks where Epcot has like 35 booths. There are also the demonstrations etc. but I have never done those.
We just did CA's food and wine festival last week for the first time, it was OK, but we much prefer the festival at Epcot. The samples did seem to be a bit larger at the CA event though so that was nice.
DCA’s as its 8 miles from my house. I’ve only been to each once and Epcot’s has more choices but the portions here seemed bigger. As far as taste, both amazing.