Comparison of exclusive decay rates forb→uandb→ctransitions

We present a variety of estimates for nonleptonic and semileptonic few-body decays of the B meson which indicate that b{→}u transitions tend to produce multibody final states. This implies that channels such as B{→}{π}{π} or B{→}{π}{ρ} offer little chance to improve the current upper bound on the b{→}u Kobayashi-Maskawa matrix element. Also the leptons in b{→}u semileptonic transitions tend to be emitted together with massive multibody states rather than a single {π} or {ρ}. This makes the b{→}u spectrum somewhat softer and the task of distinguishing such leptons from B{→}Dl{ν}, say, more difficult.