The article presents research on glass and carbon fiber reinforced plastics. The main and side surfaces of the composites were machined using face milling. A milling cutter with polycrystalline diamond inserts was used for the research. The composite materials were tested under variable milling parameters for two types of surfaces and two polymer composites. A novelty presented in the article is the comparative study of the main and side surfaces of two composite materials using 3D topography maps and material bearing ratio for the same milling parameters. The paper also includes plots showing roughness parameters as a function of changing technological parameters for two composite machining areas. The research showed that a small feed per tooth and a high cutting speed have a positive effect on surface quality. The lowest roughness parameter value of Ra 0.72 µm was achieved for the main machining of a glass fiber reinforced plastics with a feed per tooth of 0.05 mm/tooth. A high feed per tooth of 0.60 mm/tooth resulted in Ra roughness values of 2.32 µm for the carbon fiber reinforced plastics. A high cutting speed of 600 m/min during the machining of the main surface of the glass fiber reinforced plastics allowed Ra=0.52 µm to be achieved. In contrast, a low cutting speed resulted in a Ra roughness value of 1.85 µm for the side machining of the glass fiber reinforced plastics. The paper also presents material bearing ratio and 3D topography maps, which also confirm that a low feed per tooth and high cutting speed have a positive effect on surface quality.