Since the discovery of Surface Enhanced Raman Spectroscopy (SERS) and the proven ability for this technique to detect molecules at trace level, numerous techniques have been reported for fabricating substrates that ensure reliable and reproducible SERS signal on its whole surface. In this paper we studied the capabilities and sensing performances of three commercial SERS substrates (RAM-SERS-SP from Ocean Optics, QSERS from Nanova Inc. and Hamamatsu from Hamamatsu Photonics) by using diluted solution of 4-mercaptobenzoic acid (MBA) at two different excitation wavelengths (633 and 785 nm). Large datasets were obtained through Raman mappings collected randomly on different areas on the substrate surface. The averaged SERS signals for one specific vibrational band of the MBA were used to compare limit of detection (LOD), limit of quantification (LOQ) and sensitivity of the three substrates. LOD and LOQ between 1 μM and 10 μM were calculated with a range of use of only one or two orders of magnitude. The best sensing performances were reached by the Hamamatsu substrate for an excitation wavelength of 633 nm.