I think they'll both do well. it depends on the use case.

I think tribes favors organized businesses where as SMTs are basically for anyone just screwin' around.

With a tribe you have your own domain and control of the website. For most SMTs you'll just be using steemit.com. So, if you manage a millenial trans furry history group then SMTs are the spot you'll want to be. If you're managing a brand I think Tribes make more sense. All that said i still imagine people will get both. Some ease of use for posting as an SMT and ease of use for trading as a SE token.