This article by innovationcreators is a must read if you are new to blogging and have wondered which one to go for. The author used Google Trends, the latest tool by Google, to track popularity or trend of different platforms.
Thank God I have made the right decision 8 months ago on WordPress. If you are not on the right track, switching is easy.
One thing to note is author's comment on Ruby on Rails I'm sure it's catching up fast. That proves my gut feeling as well. I have recently tried Typo which runs on RoR.