WHIP and BB/9 for all four relievers, last two seasons:
Papelbon: 0.96, 1.9
Chapman: 1.06, 4.3
Davis: 0.81, 2.8
Kimbrel: 0.97, 3.6
Papelbon is less likely to give up walks, that is true. But he doesn't "blow anyone out of the water" in anything else, especially not WHIP. And the other three are so much more overpowering in terms of K/9, BAA and hard contact allowed that it's not even fair.
Stop making stuff up. You tend to do this whenever you're fixated with a player (usually a member of the Royals) and it's incredibly annoying. What you literally said is that you'd take Papelbon over anyone else in a postseason game (don't try moving the goalposts now) and that's just beyond ridiculous.