Resonant terahertz filters in microstrip lines have been proposed as devices suitable for the detection of the properties of overlaid dielectric materials, with potential applications including the on-chip assay of DNA and other biological molecules. Here, we provide a direct comparison of numerical simulations to calibrated experimental data obtained on our resonant structures. We employ two different codes (HFSS and Sonnet) to cross-check the results of our numerical simulations, and conclude that stub-based THz band-stop filters offer an improvement in sensitivity (of order 100x) per unit active area compared with alternative designs. This is a result of the enhanced THz electric field concentration in the overlaid dielectric which this particular geometry produces.