It could depend on what your other day is. I agree with OB1 that DHS is busy every day while Epcot tends to be much busier on the weekends (at least in weeks when all the parks don't fill up every day). But if I was staying into the evening, I'd avoid Epcot more on a Friday or Saturday than on a Sunday. I understand many locals go to Epcot on Friday and Saturday evenings. So, if the choice is, say, Epcot Friday and DHS Sunday or vice versa, I'd go to Epcot on Sunday. But if the choice is Epcot on Monday and DHS Sunday or vice versa, I'd go to Epcot on the weekday.