If you have strong radiometric distortions from topographic features, you can also correct for Terrain Flattened Gamma0 in SNAP.
Have a look here:
- Radiometric & Geometric Correction Workflow on the options of calibration
- Radiometric & Geometric Correction Workflow on Beta0, Sigma0 and Gamma0
- S1 radiometric correction on the effect of Terrain Flattening on images