We've been to WDW 3 different years over the 4th of July - each one we spent at MK - it's crowded, but not unbearable, and it's FUN! You can't beat the fireworks from inside MK on the 4th - they are over the castle and over the front entrance, so if you are on main street, they are in front of and behind you - and THEN, just before the finale, the park is RINGED with fireworks and you are in the center. The crowd makes it even more fun. (last 4th the crowd chanted USA, USA - very emotional time). I would definetely go on the 4th and be inside MK!