Best Wishes, hands down for me, seriously, it's no contest.
I think a lot of the great fillers in BW come from the fact that the writers aren't using Team Rocket as plot devices anymore. Them not appearing in every episode is possibly one of the best decisions ever made in this show. Their presence isn't needed in every episode and the writers are more than capable of crafting a colorful and fun palette of filler episodes without relying on the tired Team Rocket thief outline for the majority of them. I thought it was particularly awful in DP.(Which I thought had some of the worst fillers ever, Like it or Lup It! for example was an awful filler.)
Some notable fillers I really like in BW are Scraggy and the Demanding Gothita!, Scare at the Litwick Mansion!, Beauties Battling For Pride and Presige!, Dancing With the Ducklett Trio!, The Lost World of Gothitelle, Beheeyem, Duosion and the Dream Thief!, even the incredibly lukewarm plot-idea episode known as Lost at the League! was made somewhat amusing by the interactions between the core group of Pokemon. That's the thing I like about these fillers, the characters and Pokemon, the interactions tie everything together so well. These fillers either have an entertaining human or Pokemon or both in the mix which was a rarity before BW in my eyes, they all usually have fun or cool personalities that keep me invested in them for 22 minutes. Selfish Gothita, troll Ducklett, the Dream thief, Katharine, the homicidal Litwick, the spoiled girls known as Moira and her clique, they're all usually so entertaining and engrossing from start to finish.
When it comes to wacky, crazy, insane and unique things these fillers never disappoint for me. I'm glad the writers shook off the poisonous stale filler formula left behind by the last series and tried something new.