I am building a 12' x 10' deck. I am pouring concrete columns, and using post brackets. The posts will be about 4' tall. There will be 9' between them. They will support a beam that the joists will sit on. Is it better to use a 4"x6" post, or a 4"x4" post? This deck will be located in Michigan. I only have access to brackets for a 4"x4" post. So would there be any benefit to using the bigger post? If I could get your oppinion, and or experiences with both that would be much appreciated.

Thank you