Having seen both recently, I would vote for The Ferryman. I really enjoyed much of The Waverly Gallery, but the play had these long transitions where you would be staring at a brick wall for a full minute, which really interrupted the flow of the play. I appreciated the performances and the writing, but those scene changes really just threw a wrench in the storytelling. This may seem like a minor thing to quibble over, but it really did impact my ability to emotionally connect to the show when I was yanked out of it every 5-10 minutes or so. The Ferryman was expertly directed, written, performed, and designed. Additionally, the scale of the play (21 actors plus a few animals) means that it won't be programmed by very many regional companies in the future. For me, The Waverly Gallery was good, but The Ferryman was thrilling.