For the Jacobi family with parameters (0,β), β≥−1/3, we prove a continuous comparison theorem for the associated weighted Jacobi-Radau functions. When two consecutive functions are parametrised by the same Prüfer phase, the function of higher degree attains that phase closer to θ=0 and has strictly larger amplitude. In particular, the moduli of all corresponding relative extrema increase strictly with the degree. The lower bound −1/3 is sharp for this continuous statement: when −1<β<−1/3, the amplitude inequality is reversed at sufficiently small positive phases. This local reversal does not determine the optimal range for the discrete extremal inequalities. For −1/3≤β≤0, the positive Jacobi product formula identifies the endpoint values of the Lebesgue functions with the global Lebesgue constants, so (Λ(0,β)n)n≥0 is strictly increasing. At β=0 the weighted Radau functions reduce to P(0,−1)m. We thereby recover the theorem of Wong and Zhang and obtain, through an exact total-variation formula, a short proof of the Qu-Wong theorem on Legendre Lebesgue constants. The representation and the termwise comparison together realise the alternative-expression approach proposed by Qu and Wong, without asymptotic expansions, error bounds, or finite numerical verification. The proof is based on the equal-phase Prüfer architecture developed in the first author's earlier preprint arXiv:2608.01404; it applies that architecture to the problem posed by Qu and Wong.