Recently, within the emerging framework of “lab-on-fiber” technologies, we successfully demonstrated the integration of phase-gradient plasmonic metasurfaces on the tip of an optical fiber. The resulting optical-fiber “meta-tips” promise to empower the typical fiber-optics application scenarios (e.g. sensing, telecommunications, imaging, etc.) with the advanced light-manipulation capabilities endowed by metasurfaces. Here, we explore more in detail the possibility to exploit this platform in label-free biological or chemical sensing applications. Specifically, we carry out a parametric study of the surface sensitivity and show that phase-gradient metasurfaces generally outperform their gradient-free counterparts, without imposing additional fabrication complexity. Therefore, the phase gradient can be effectively exploited as an additional degree of freedom in the design of high-sensitivity devices.