I voted for Le Cellier on the assumption that you'd actually be at EPCOT. We've eaten at LC twice for lunch and loved it but I wouldn't go out of my way to get there. Now...if you're hanging around OKW I'd vote for taking the boat to DTD and having lunch at Wolfgang Puck Cafe which is the TS restaurant on the West Side. We just ate lunch there yesterday (before we left ). It has my favorite dish - pumpkin ravioli with chicken ....they also have great sandwiches on the lunch menu, too.
A few years ago I would have said Olivia's. Our first visit to OKW we liked it so much we went back a second time. Unfortunately we have since had two very poor experiences at Olivia's. I know that can happen, which is why after the first one we went back again, we figured it had to have been a bad day. After two bad dinners on seperate vacations, we felt there were so many options at WDW we would not go back to Olivia's.