The common application of Synthetic Aperture Radar Image Processing is the Automatic Target Recognition. How does it compare to the Quality of Optical Image Processing?
1) research trends - mixed instrumentation + information fusion from active and passive sources
2) IP is very rich research field as well as SAR IP is. An IP performance is different with various data, fusion levels, processing pipeline, class of algorithms. To answer more accurate, the question should be focused on specific target group (in selected static/dynamic conditions) and cover more specific domain.
Sources of insight:
try to start from an old but comprehensive survey http://www.mdpi.com/2072-4292/5/2/716
books:
Mathematical Models for Remote Sensing Image Processing: Models and Methods for the Analysis of 2D Satellite and Aerial Images, Springer, 2017, http://www.springer.com/gp/book/9783319663289