Having used Mastodon and Micro.blog now, my feeling is that there’s room for both because they’re trying to do different things. Mastodon wants to be a better, distributed, and more thoughtful version of Twitter. Micro.blog is just blogging with a social layer laid on top of it. It supports using a Micro.blog hosted site as your regular blog, like Wordpress or any other system, and not engaging with the social layer at all. Or, you can put your blog wherever you like, connect it to Micro.blog, and just use it for the social layer. They both want to be more and less ambitious than one and other in entirely different ways. Mastodon wants to be bigger, where Micro.blog could stay relatively small and still be successful as long as people are using it to blog and interact.