Field cooling of photovoltaics typically entails a sole thermal or electrical effect evaluation, even though rear heat sink becomes beneficial when lowering module temperatures, improving their uniformity, and retaining their current-voltage point simultaneously. In this study, the question is investigated about the preference of a truncated multi-level fin heat sink over other rear structures of PV modules in case when temperature effectiveness, thermal uniformity, and electrical parameters are considered as a coupled decision problem. The comparative analysis is based on an outdoor data set of two monocrystalline photovoltaics having the same nominal power (120 Wp). One is a reference module without any additional features; the second module is equipped with an aluminum extrusion multi-level fin heat sink on the rear surface. Ten criterion measures include cooling effectiveness, three irradiance-dependent uniformity criteria, short circuit current, open circuit voltage, maximum power current, maximum power voltage, maximum power value, and fill factor. Grey Relational Analysis is employed to convert all heterogenic measures into criterion coefficients and integrated grade values. Sensitivity of ranking to changes of distinguishing-coefficient and weighting values is estimated in four different scenarios: thermal-only, electrical-only, domain-balanced and distinguishing-coefficient. The finned module offers 8.45 °C maximum effectiveness coefficient, higher uniformity index value at 520 W/m2, 940 W/m2, and 640 W/m2, improved open circuit voltage by 1.4 V, maximum power by 9.38 W and fill factor by 0.06. Short circuit current is the sole disadvantage of a fin structure, being slightly greater than that of the reference module. Under equal criterion weights and ζ = 0.5, the grey relation grade values are 0.933 and 0.400 for the finned and reference module, respectively. The order does not change in any other sensitivity scenario. The results provide a clear answer to the posed question: a truncated multi-level fin is the superior configuration as far as thermal and electrical performance are concerned.