This manuscript presents a comparative biosensing analysis of a dielectrically modulated dual-drain vertical TFET (DD-VTFET) by considering three distinct device arrangements based on the cavity position. DD-VTFETs with single cavity at the source and drain edge are called SC-DD-VTFET and DC-DD-VTFET, respectively, while for SDC-DD-VTFET, dual cavities are created at both the source and drain edge. Asymmetry in cavity position results in different electrostatics for each biosensor, leading to variation in their sensing performance. The on-current sensitivity is found to be lower for the DC-DD-VTFET due to the absence of cavity near the channel-source interface, while the SC-DD-VTFET shows poor performance in terms of ambipolar current sensitivity compared to the SDC-DD-VTFET. Moreover, the study includes the consideration of neutral and charged biomolecules (both positive and negative) with varying dielectric constants of 5, 7, 10 and 12. The sensitivity of partially filled nanogaps with fill-factor (FF) of 42% and 60%, influenced by steric hindrance, are also compared for all three DD-VTFET based biosensors which includes different step profiles of biomolecules, such as concave, convex, increasing, and decreasing. To consider the non-ideal state of the DD-VTFET based biosensors, the effect of irregular placement of the probe within the nano-cavity on different sensitivity parameters for a particular k-value of biomolecules is also analysed using TCAD simulator. Furthermore, the performance of the DD-VTFET based biosensor is quantitatively benchmarked against previously published works available in the literature. For a fully filled cavity with neutral biomolecules having dielectric constant of 12, SDC-DD-VTFET based label-free biosensor provides ON-current and current-switching ratio sensitivities approximately in the order of 105, while the ambipolar current sensitivity of 2.1×103 is observed which makes the sensor equally suitable for sensing the biomolecules even at negative gate bias.