When we are hosting a wordpress blog , it offers us very limited flexibility (though greater than that of blogger) compared to what it offers to you when you use a self hosted wordpress blog (your own domain, your hosting and code from wordpress.org) for example you can modify CSS, you can modify the template - even write your own php over the wordpress framework.
The recent problem that I've faced is that of performance of self hosted wordpress - because it creates a load on the database because a good traffic hits the database again and again and unless you have enabled good amound of caching, you'd be doomed. I have the best hosting service provider in India (Hostgator) and even they complain about the load. However, this might sound a little to techy.
In general, wordpress.com blogs are better than blogger but people tend to use blogger because it's easier to get accustomed to it. Tumblr is good and easy to use (the android app is also nice) but I have not seen any means to export or import blog like blogger or wordpress. Export works best with wordpress.