We report a comparative analysis between InGaAs and GaAsSb-based top-down cylindrical nanowire arrays fabricated from p-i-n heterostructures. Optical constants measured via spectroscopic ellipsometry were incorporated into FDTD simulations to optimize array geometries. Simulations indicated that GaAsSb nanowire arrays with a diameter of 314 nm and a period of 904 nm achieved a peak absorption of 98% at 1550 nm, while InGaAs nanowire arrays with a 326 nm diameter and 1090 nm period reached 76%. Measurements of fabricated arrays showed absorption of 89% at 1628 nm (GaAsSb) and enhanced sub-bandgap absorption at 1766 nm (InGaAs) at room temperature. These results were confirmed through modelling of the as-fabricated nanowire diameters 330 nm and 411 nm, demonstrating excellent agreement between theory and experiment. In both material platforms, nano-structuring improved the absorption relative to planar films, demonstrating near-unity absorption suitable for practical single-photon detection.