WordPress is a flexible solution for web publishing. Post Formats were introduced a couple of years back to help users and developers to create content in one WYSIWYG Editor but show it differently on the site. I’ll start by saying that there is quite a bit of press about why there is a general lack of support by theme developers for post formats (see one example below).
– If you have a theme which doesn’t support post formats (most don’t) then you can’t start this way. Developers are not adding them as Custom Post Type is the more flexible solution (for managing and displaying content of different ‘types’).
– From a development perspective, if you want to write a query to just find posts of the format Aside that is easy, but to find just standard posts you have to do a query to exclude post formats aside, quotes, etc, etc, etc). So it’s a pain to code for.
– If you wanted to have different themes, views and layouts and domains, for each content type, then that’s far easier to do with WordPress multisite network and much harder with post formats
– All post formats (asides, standard, quote, etc) are included in your WordPress loop so by default they will get included in any RSS feeds or custom WP queries, which means you end up un-necessarily, having to re-code ‘a lot’ to exclude post formats from places where you don’t want them to show.
– Which reminds me, WordPress MU Sitewide tags will allow you to agregate all content from your sites into one master blog. This is what I do if you have a look at http://wordpress.damien.co and http://damien.co