Extratropical cyclones are a key driver of midlatitude weather variability, including high-impact events with heavy precipitation and severe wind gusts. Cyclone intensification results from the complex interplay of baroclinic dynamics and diabatic heating, the latter being closely linked to cloud-related processes within warm conveyor belts (WCBs). Focusing on four representative intense European cyclones, this study contrasts two commonly used methods — pressure tendency equation (PTE) and piecewise potential vorticity (PV) inversion — to assess the methodological uncertainty in quantifying the role of diabatic processes for cyclone intensification. The methods are complemented by a deep learning-based WCB identification diagnostic. Although for most cyclones PTE and PV inversion yield consistent results regarding the role of diabatic processes, substantial differences are found for at least one cyclone. Cyclones with strong diabatic heating contributions tend to be associated with enhanced low- to mid-level PV forcing. For two diabatically influenced cyclones, PV contributions are concentrated in the frontal circulation. In contrast, for one cyclone, the mid-level forcing is more strongly linked to shear in the jet region rather than diabatic heating. Overall, our results demonstrate the benefit of combining complementary diagnostic approaches to better constrain the contribution of diabatic processes to extratropical cyclone intensification. The clear link between the diagnostics highlights the potential of both methods for systematic evaluations of weather and climate models.