I am going to guess that the entire trip, with the three hotel stops, takes around 25-30 minutes. There is no question that you can walk the distance and beat the boat. The only time the boat is faster is IF you get one right away and it leaves immediatley, AND you are only going to the Swan/Dolphin. Under any other conditions walking will win.
When we stayed at the Yacht Club two years ago we always beat the boat back with normal walking.
We never walking the entire distance from the Studios to Epcot. I would suggest anyone going the whole route is better off taking the boat.