I prefer Joomla. Though, to be honest, I have seen them both used for corporate websites in the past.
i like joomla. It have many nice Templates, Module & Component. You can view : http://freecode4u.com/forums/joomla-mambo/
It all depends on what you are looking for in the CMS. I've been using both Joomla and Drupal. But as loads of people I prefer using Joomla rather then Drupal. Not saying that Drupal is bad, its as good as Joomla. But if you get used to one thing, you start using it more often.
For Ecommerce site, use a Ecommerce plattform such as: http://www.magentocommerce.com/. I've been working with commerce site using Joomla, but I dislike it, because commerce system is not good enough for professional players.
First, I'm a Joomla fan. I respectfully and strongly diagree with the poster who labled it a POS. I manage dozens of Joomla sites. That being said, If it's primarily text content, probably Drupal. But if you want it to be a feature rich higlhly flexible site with the ability to plug in tons of neat gizmos ... (which I LOVE) then go with Joomla.
Joomla! is a piece of crap. I've developed with it and drupal and drupal has far more scaleability and is many times faster than joomla. Ubercart and the Ecommerce module for drupal far exceed that of virtuemart for joomla... I know I've used both. The amount of flexibility and granular security make Drupal a #1 choice every time for me.