I've found that unless you get on a boat that's sitting at the dock when you exit the Studios, walking *always* beats out the boat.
Even if there *is* a boat there, it'll be about the same as a strolling pace along the walkway. A decent-pace walk will most definitely beat the boat in a race to Epcot.
Fastest route while walking:
As you walk along the path, turn into the *themed* pool area (with the coaster water slide), walk around to the far side of the pool and then cut through to the main part of the Boardwalk. Then continue to the right around to Epcot. Doing this cut-through cuts about 1/4 mile off the walk up and around the far end by Atlantic Dance and Jellyrolls.
-Rob