...In KC, they don't really need a loogy--their late inning power righties are so good. Buck, however, has a bunch of good lefties. Cubs probably will lack really good lefties in 2015 but guessing not a priority this off-season, with Vizcaino and Rivero joining the other power righties....
An advantage of a deep, good RH pen is that usage is less complex. Renteria did very little righty-lefty-righty mid-inning matchup switches, mostly full-inning outings. Guys have less appearances; guys always have time to warm up adequately; no "wasted" warmups. Probably more advance planning. (V isn't pitching tonight, but we still have W, X, Y, and Z available, and using them isn't like giving the game away.) Games go faster, too, and probably less mental strain on fans, manager, or relievers.