Surface enhanced Raman spectroscopy (SERS) is a powerful non-invasive technique to detect and identify molecule traces. The accurate identification of molecules is based on the detection of distinctive vibrational modes characteristic of a molecule adsorbed onto the surface. We investigated the detection performances of three commercial SERS substrates: nanostructured Au supports from Hamamatsu, Premium Ag–Au supports from SERSitive, and RAM–SERS–Au from Ocean Insight, which were tested with solutions of thiophenol (C6H6S) at 10–6 M and 10–8 M concentration. SERS measurements were performed systematically with 633 and 785 nm excitation wavelengths and Raman mappings were recorded randomly on the surfaces. The spectral quality (baseline intensity and signal-to-noise ratio), the thermal stability under laser illumination, and the Raman intensity distribution of the Hamamatsu substrate and our own fabricated gold substrate were discussed for the detection of 10–8 M thiophenol molecules. The detection of crystal violet (CV), a toxic dye, is demonstrated at 5.10–9 M.