In my opinion, the best bus service is the resorts that have direct service to a park, and it varys with levels of resorts.
I guess the best then would be Pop Century and it's transportation to MK, Epcot, and Studios. No other stops. However, it's transportation to AK is not as good, because it also stops at Blizzard Beach.
AKL is probably about the same because no sharing either. (I think the Studios run is the one that stops at Blizzard Beach).
Carribbean beach and OKW seem to be the worst to me. Many, many stops within the resort. I hate that, and at Carribbean Beach you NEVER know whether your stop is #1 or #8 because it varies because of where the bus entered Carribbean beach. (They have like 4 bus entries).
I used to recommend that folks go to the Contemporary instead of TTC to park hop from MK, however, don't do that to go to the Studios, because that bus also stops at the Poly and the Grand Floridian, yuk!!
Also, the Epcot Resorts have strange bus service also. They all share buses for many routes. If I could figure out what resort is their LAST stop before heading to their destination, I would be happy, but there seems to be no rhyme or reason. For awhile the last stop was Yacht Club before heading to DTD, however my last trip the Beach Club was the last stop.
Also, all of this also depends on time of day and time of year. Rush hour, there may be no sharing (park opening and park closing), but middle of the day, very early morning, and the last few lets clear the park, may have sharing.
I guess you can tell I don't mind waiting for buses, but once I get on one I really prefer it to go directly to my destination.
Another thing is the Disney transportation service, especially the bus service is very dynamic and adjusts to the conditions of the moment, so you can never really say that any one resort has the "best" bus service all the time.