I presume you mean hosted, then? At Blogspot.com or WordPress.com? Believe it or not, my only externally hosted blogs are on Blogspot.com, and I've never tried WordPress.com. I'm all about "rolling your own" and run WordPress independently. Close to fifty installs across several servers and clients, actually.
I'm a WordPress evangelist and would recommend its hosted solution just on principle, but I can't really speak as to its functionality when someone else is running it.
Yes - hosted. I was considering running WordPress on a company server so I could hack it, but I couldn't come up with any new features to justify the effort. Everything I need seems to be covered by the core platforms and their plugins. Why are you hosting your own installations? Is it because of quotas on the hosted solutions? Are you adding new features?
These days I am a big fan of hosted solutions. We used to host everything for customers but these days we typically use hosted solutions for almost everything. You just can't beat the cost and convenience. We use Google for email and calendaring, Atlassian for wiki hosting (Confluence), and Rackspace or GoDaddy for web applications depending on the application requirements. These services get better and cheaper every year.
I have used both of them and I definitely prefer WordPress over Blogger because WordPress has greater widgets selection.
However, my main complain about WordPress is that it does not allow any code that includes Java, so you cannot embed fun Java script widgets such as Shelfari. WordPress automatically suppresses them. A solution is to host your blog outside of WordPress and just use the WordPress script to create your blog. (I wish I had known that before signing up for hosting!)
A current issue about using WordPress is that you cannot implement Google Analytics into it (when hosting your blog at WordPress) because 1) the updated, non-Urchin code is Java based and 2) the Google Analytics code is already implemented into every blog via the WordPress Blog Stats. WordPress claims that the Blog Stats are good enough. I strongly disagree. There is a strong push to create a Google Analytics widget.
Despite these two issues, I strongly recommend using WordPress over Blogger because it makes blogging a snap!
Check out my WordPress blog at www.idaconcpts.com, here we we put ideas and concepts to work in web analytics.