Kirby's Up-B 3 seems like the safest recovery option and makes his off stage game seem really ridiculous with almost no down-side (could be paired really well with the Down-B 3 and its spike). Considering how useless I thought his Up-B was in Brawl, I will definitely be using Up-B 3 whenever custom moves are allowed.
Neutral-B 3 seems like it could be used near the edge of the stage and can be used to punish landings and put characters with a worse recovery than you into bad situations if you spit them out further away from the stage. Otherwise I would stick to Neutral-B 1.
Down-B was always gimmicky, but I NEVER used it against anyone that was grounded, which makes Down-B 2 seem useless to me. I will probably always pick Down-B 3 because of the off-stage punish that is suddenly more realistic with the new ledge mechanics. A spike sounds better than sending them at an angle and giving them more of a chance to recover.
Side-B 2 seems like the obvious choice for me because of aerial hammer and it seems to be the fastest out of the three hammers.