Let’s look at WordPress, Blogger, and Square Space. Square Space isn’t a blogging platform per-say, but rather a website editor with blogging tools. One can argue this is what wordpress has tured into anyway.
If I were to rank these for blogging I’d probably put then Blogger, WordPress, and then Square Space. The reason being is, with blogging you really only need an easy publishing tool, and it doesn’t get much easier than blogger. It’s straight forward, easy to use and really only does one thing. WordPress has evolved into a very in-depth web authoring tool and as such can be a bit harder to hit the ground running. Square Space has blogging as a feature more than anything else.
If I were to rank these by best overall tool however, I’d probably put them WordPress, Square Space, and then Blogger. WordPress is extreamly extensible, has access to probably millions of plugings, and the source code is 100% editable. It’s easy to stand on the shoulders of giants with WordPress and make some amazing things. Square Space is a great authoring tool, with some amazing built in customization features, but is a bit less open to edit. Blogger is very limited and very hard to edit. I’ve had experience with how cumbersome it is.
When choosing one though you still have to factor in other things, like the fact that Square Space isn’t free. Blogger ONLY runs on it’s platform and the underlying code I don’t believe is customizable at all. The large majority of developers know wordpress (at least some what) and could help if needed. These are just some other factors that come into play when choosing one.