= Solution
Use the supplied surface <temperature>, $420^\circ\mathrm C\simeq693\,\mathrm K$, as the premise. With otherwise comparable material and <geothermal gradient>, this hotter boundary increases thermally activated <material creep> at shallow depth and places a chosen mechanical cutoff <temperature> closer to the surface. That effect alone would favour a thinner elastic layer than in a cool terrestrial oceanic plate.
<Water weakening of rocks> makes dryness act in the opposite direction. Water can enhance <material creep>; sufficiently dry material can remain strong at temperatures at which its wet equivalent relaxes. Experiments on dry diabase provide a concrete basis for a strong dry <crust> and possible mechanical coupling between <crust> and <mantle>, rather than requiring a weak crustal layer solely because the surface is hot.<High-temperature deformation of dry diabase, with application to crustal deformation on Venus by S. J. Mackwell and others>[1996, printed pages 793–794, dry strength and implications for crustal coupling]{ref}
For an illustrative steady conductive geotherm with <thermal conductivity> $k_T$ and <heat flux> $q$, a fixed strength cutoff gives
$$
T_e\sim\frac{k_T(T_*-T_s)}q.
$$
Therefore the comparison would scale as
$$
\frac{T_{e,V}}{T_{e,E}}\sim
\frac{k_{T,V}}{k_{T,E}}\frac{q_E}{q_V}
\frac{T_{*,V}-T_{s,V}}{T_{*,E}-T_{s,E}},
$$
where all temperatures are compared consistently and a dry rheology may have a higher effective cutoff $T_{*,V}$. This is a conditional strength-layer estimate, not a universal definition of $T_e$.
\b[<Venus> can retain appreciable <elastic thickness> despite its hot surface; <temperature> favours thinning, while dryness favours strengthening. The supplied facts alone determine neither a numerical $T_e$ nor a definite ordering relative to <Earth>'s oceanic plates.] The comparison requires heat flow, subsurface thermal history, material rheology, interior water content and loading timescale. Little atmospheric water is evidence relevant to the hypothesis of dry rocks, not a direct measurement of deep water activity.
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