We like BW, we stayed at YC once a long time ago but it hasn't changed much.
BW is last boat stop for Epcot and first one coming back so it's a really short boat ride. Of course, that also means it is the opposite for DHS and it's the longest. YC is the middle stop in each direction.
The walk from the boat launch to the lobby is about 1/5 the distance vs. YC.
Boardwalk has much more to do, there's the Bakery, Candy/Sweets Shop, a few stores, plus bars and restaurants. The games are pretty small and expensive. We love being able to sit out on the Boardwalk with a Red Rocket Ale at Big River Grille in the evening. At YC, there's some benches outside the lobby and along the water, but not much else besides Beaches & Cream.
The atmosphere is great at Boardwalk. You feel like you're "somewhere" and not just a hotel.
Overall, BW wins for us, by a longshot!!