Gamma-ray burst prompt detection rate as a function of the EM detection limit threshold for our fiducial NSNS (left panel) and BHNS (right panel) populations. We account for the Fermi/GBM duty cycle. In each panel we report in orange, grey and black the ETΔ, ET2L and ETΔ+2CE configurations, respectively. The solid line indicates all the detectable binaries, the dashed and dotted lines the detectable binaries with ΔΩ_90% < 100deg² and the ones with ΔΩ_90% < 10deg², respectively.