  We calculate the independent helicity amplitudes in the decays $B \to K^*
\ell^+ \ell^-$ and $B \to \rho \ell \nu_\ell$ in the so-called
Large-Energy-Effective-Theory (LEET). Taking into account the dominant
$O(\alpha_s)$ and SU(3) symmetry-breaking effects, we calculate various Dalitz
distributions in these decays making use of the presently available data and
decay form factors calculated in the QCD sum rule approach. Differential decay
rates in the dilepton invariant mass and the Forward-Backward asymmetry in $B
\to K^* \ell^+ \ell^-$ are worked out. We also present the decay amplitudes in
the transversity basis which has been used in the analysis of data on the
resonant decay $B \to K^* J/\psi (\to \ell^+ \ell^-)$. Measurements of the
ratios $R_i(s) \equiv d \Gamma_{H_i}(s)(B \to K^* \ell^+ \ell^-)/ d
\Gamma_{H_i}(s)(B \to \rho \ell \nu_\ell)$, involving the helicity amplitudes
$H_i(s)$, $i=0,+1, -1$, as precision tests of the standard model in
semileptonic rare B-decays are emphasized. We argue that $R_0(s)$ and
$R_{-}(s)$ can be used to determine the CKM ratio $| V_{ub}|/| V_{ts} |$ and
search for new physics, where the later is illustrated by supersymmetry.
