In the field of gas sensing, many commercial laser-based instruments rely on absorption measurement for gas concentration retrieval. However, there is a niche for dispersion techniques with unexplored potential. In this work, we provide a thorough comparison of the following spectroscopic techniques:  Tunable Diode Laser Absorption Spectroscopy (TDLAS)  Wavelength-Modulation Spectroscopy (WMS)  Heterodyne Phase-Sensitive Dispersion Spectroscopy (HPSDS) For the HPSDS technique, instead of quantifying the attenuation of laser intensity, we measure the phase shift of the laser beam introduced by the gas dispersion. Dispersion measurements promise baseline-free operation, a linear relationship between phase and gas concentration, and immunity to power fluctuations. Transitioning between these techniques requires minor electronic modifications, while the optical scheme remains unchanged [1]. For system design, we employ a 31m Herriot cell from Thorlabs and a 4.55μm ICL laser from NanoPlus. Figure 1 presents initial linearity comparisons. To date, there is a limited number of such comparison studies available [2, 3]. With this work we aim to provide a review that will benefit the community in choosing the appropriate technique for future projects. References: [1] Martín-Mateos, Pedro, et al. "Heterodyne phase-sensitive dispersion spectroscopy in the mid-infrared with a quantum cascade laser." Analytical chemistry 89.11 (2017): 5916-5922. [2] Lins, B., et al. "Simulation-based comparison of noise effects in wavelength modulation spectroscopy and direct absorption TDLAS." Applied Physics B 100 (2010): 367-376. [3] Genner, Andreas, et al. "A quantum cascade laser-based multi-gas sensor for ambient air monitoring." Sensors 20.7 (2020): 1850.