ergophobe - 6:20 pm on Jan 17, 2013 (gmt 0)
What's your timeline?
I think Wordpress has some strong mobile initiatives.
Drupal is aiming to make Drupal 8 a "mobile first" CMS and prioritize mobile and responsive design. The goal is to make it the best open source mobile CMS, but Drupal 8 doesn't even hit code freeze until July 1, 2013