The aim of this work is to highlight the differences and the similitudes between two different platforms for GPUs’ coding, CUDA (Compute Unified Device Architecture) and OpenCL (Open Computing Language). The work will be explained further through a practical example, exposing how is organized the code of an actual SAR (Synthetic Aperture Radar) focusing system and showing the highlights and weaknesses of such system in comparison to a different coding of the same system. In conclusion, the main key points of the two different approaches applied to the SAR focusing system will be analyzed. Actually, both platforms are largely used and each of them has its highlights and weaknesses, so they are both used but for different aims and targets.