I have been a massive fan of using Seesaw and discuss it a lot on my training and inset. I have flirted with Showbie, which is a similar app, and seen some wonderful ways it has been used in schools. In my experience, one thing most primary teachers are looking for is simplicity! Seesaw stands out to me because it is so simple and easy to use.
More information about the blogging feature can be found here -http://web.seesaw.me/blogs/