The YC dock is about 0.1 miles from the lobby of the BC, while International Gateway is about 0.25 miles, so depending on where you are in the BCV, it might be pretty much the same. The advantage if going to International Gateway is that you're at the start of the route so you should get a seat. If you wait until YC, folks from Epcot and the BW will have already boarded.
It is further to get to the front of Epcot where the buses are located. You have to enter via International Gateway, then walk to the front of Epcot. It's at least three-quarters of a miles. You can't walk from the BC to the front Epcot without going through International Gateway, so you'll also need park hoppers.