We are traveling next week to WDW and were originally planning on doing MK on Monday and Epcot on Tuesday. But the wait times this week are making me rethink this plan and switching days. We aren't doing park hoppers so it's one park a day. Opinons?? I will add I have an ADR for Monday at BOG I would loose by switching days...
Depends on a couple of things: are you planning on rope drop, or staying late, watching fireworks, going to
MNSSHP, age of kids, how long is your trip, if you'll have other days at the parks, etc. Monday will be busy with resort guests in morning because of EMH, and busy during the day with onsite and offsite guests because it's Monday, and busy at night because with so many parties there are only three nights per week for people who aren't going to MNSSHP to see Wishes. MK will be much less busy Tuesday morning, but will start to get more busy when MNSSHP guests start showing up around 4pm. I'm usually less worried about Epcot crowds, fewer rides and it's easy to do just about everything in Future World.
I'd say if you are morning people, and have no problem getting to the park before 8am for EMH rope drop, you can certainly do MK Monday and Epcot Tuesday. But after 10:30am or so, lines will be much longer than if you swapped your park days, but that would mean losing your BOG ADR and not getting a full day at MK Tuesday.
With park hoppers you have many more options. For example, could do Epcot Monday morning without FP, then hop to MK Monday evening with 3 FP+ and to see Wishes. Then MK Tuesday morning and hop to Epcot when party guests start arriving. Or the opposite: MK EMH Monday morning, then hop elsewhere when it gets crowded.