We find the transporation options at the Poly wonderful! For us, pushing a stroller onto the monorail is 100 times easier than folding it up, trying to gingerly load it on the bus, all while attending to our four kids.
I too question some of those transportation times, I know it DEFINITELY did not take us 20 min. to get from the BWI to Epcot, and the YC/BC is closer, it is more like five-10. It took 15 minutes to get from the BWI to MGM if we walked, but not on the boat. The monorail to Epcot, including walking from our room in Hawaii at the Polynesian, was not 20 minutes, more like 15 at the most, not to mention that it is a much more enjoyable experience for us than the buses.
So, for us, the monorail makes a huge difference. We are staying at the Boardwalk this next trip and I know that we will miss the Poly! Have fun, whatever you decide!