Left: Ratio between CTA-S integral (solid) or differential (dotted) sensitivities computed for different spectral slopes α (given in the legend) of a point-like source, and the corresponding one evaluated for α = 2.0. All the curves for differential sensitivities overlap, as expected. Right: Ratio between point-like integral sensitivity (calculated for the spectral slopes indicated in the legend) and point-like differential sensitivity (multiplied by energy E*) at various energy bins centred in E*, for ASTRI, CTA and LHAASO-KM2A.