Up to you of course. I personally use Debian on the desktop as well, and would prefer something Debian based for the mobile as well. However Debian as a project is rather slow to advance much in the mobile sphere. Mer on the other hand moves fast and is optimized for mobile, being well ahead of others, so I see nothing wrong with using it. Learning different tools like RPM vs DEB or some architectural differences and etc. isn't a scary or unworthy effort.