The exclusive rare decay B→K ∗γ takes place in a region of maximum recoil, q2=0, posing a problem for nonrelativistic quark models which are usually thought to be most reliable at zero recoil. The Bauer-Stech-Wirbel (BSW) model, formulated in the infinite-momentum-frame (IMF) formalism, is designed to work at q2=0. We show in this model that the ratio relating the decay B→K ∗γ and the q2-spectrum of the semileptonic decay B→ϱe overlineν, becomes independent of the wave function in the SU(3) flavor symmetry limit. We show that this feature is also true in relativistic quark models formulated in the IMF or light-cone formalism, if the b quark is infinitely heavy. In fact, these relativistic models, which have a different spin structure from the BSW case, reduce to the BSW model in the heavy b-quark limit. A direct measurement of the q2-spectrum of the semileptonic decay cam therefore provide accurate information for the exclusive rare decay.