Berryman Professional Chem-Dip Carburetor Parts Cleaner (part #0905) has been our professional-grade, chlorinated immersion cleaner for nearly 70 years.  Its powerful, proprietary blend of solvents like methylene chloride and toluene cleans all metal parts fast without the need for heat, aeration, or agitation.  It is a very aggressive product, but it also has a bit of a persistent odor, which is disagreeable to some users.  Employment of proper personal protective equipment (PPE) and adequate ventilation are critical when using 0905.   As for Berryman Non-Chlorinated Chem-Dip Carburetor Parts Cleaner (part #1905), this product was formulated a few years ago to be a safer, non-chlorinated alternative to 0905, yet still be a powerful cleaner that is equally compatible with all metals.  It offers considerably lower toxicity and odor than 0905.  This product is also safer for indoor use but still requires the use of gloves and safety glasses.   As for which one is “better,” it depends on the substrate, the type of soil, the age and temperature of the product, how many times it’s already been used, etc.  With the 1905 being a very aggressive cleaner, yet a toxicologically safer and more modern product, that might be a “better” cleaner for many users to start off with.