The Roku's get significantly more use for me, but I do use the Chromecast's occasionally. For example, the YouTube live streams seem to still not work on the YouTube Roku app but do work on the CC. Also, use WatchABC, Comedy Central, Nickelodeon apps to cast content to the TV since none of these are available (yet) on the Roku's.
Also, Starz and Encore Play apps have CC support but are not (yet) on the Roku's.