metal roofing preference

Thanks for your interest in metal roofing. There is a lot more to consider than the metal thickness to determine a quality product or installation for that matter. There are some light gage aluminum roofs that preform very well. I am assuming you are referring to Stainless when you said 'seamless'. The metallic coating is very important. For Galvanized the appropriate designation is G-90, Galvalume it is AZ50 when it is painted. AZ55 unpainted. Aluminum is a great material to use as is stainless steel. Next thing to consider is the paint finish. The best systems hold their color and do not fade. They are known as PVDF, Kynar 500, or Hylar 5000. I caution you not to use warranties to determine the quality of a product. Using products that carry the Metal Construction Association (MCA) certified product warranty assures that quality prodcuts are used. After you have confirmed that the porduct is quality you desire, you need to research that the contractor is kowledgable in the installation of the product you have selected, this website is a good place to start. Check his BBB report. Ask for references and verify that the customers are pleased with his work. Let us know if there is anything else we can do for you.