We were at WL last week and had the same dilemma with an 8:10 am ADR at Crystal Palace. During the course of our stay, we found that the bus was much faster than the boat to get from WL to MK. The boat has other advantages, but for pure speed the bus is faster. For our early ADR, we arrived at the bus stop at approximately 7:40 am and we were dropped off at the MK entrance at approximately 7:45 am (of course, the bus happened to be waiting at the bus stop when we arrived). The bus goes directly from WL to the front of MK with no stops.