I have been using Wordpress for over 4 years so my choice is obviously! However, I think that there are few advantages in using Joomla (for example if you want to make a portal/community site), so it depends on what do you want to do.
Joomla will probably end up costing you more in the long run in terms of extra plugins and custom development, especially if you try to process payments with the site. It really comes down to what you want to do, and what's available for both to make them do that.
I feel, integration of Wordpress within Joomla! Its because I don't want to miss Joomla!'s rich features as well as WP as a best software for blogging.
I started with Joomla for a while but realized how much better I liked Wordpress for its ease of use. I'm sure Joomla is the better choice for some sites but my sites are too simple to be worth trying to design the Joomla site right.
I would say WP. it's more user and seo friendly imo. The huge range of plugins and themes make it's possibilites endless too.