When I started blogging,I didn't know about WordPress and created my blog on Blogger.Ankur suggested me to try out wordpress as it is undoubtedly a better blogging platform.I rejected wordpress at that time for reasons I don't remember.After more than 1 year of taking this decision,I'm proud of it.Although WordPress is great,WP.com has some restrictions which are a big problem for me at least.Here's a short description of these limitations-
Using your own domain
Blogger allows you to use your own domain for your blog free of cost.This is perfect for people like me,who don't intend to buy hosting for some time.On the other hand,wordpress offers this service as an upgrade and charges a monthly fee for it.Basically,unless or until you can afford/get your own hosting and use WP on it,forget about your own domain.There's no point paying wordpress more than your domain registrar as you will still be subject to other restrictions.
The WordPress policies don't allow a blog hosted on wordpress to have AdSense ads on it,I've even heard of cases where blogs have been banned/locked if they use AdSense.Blogger has no restrictions on advertising(for obvious reasons).
WordPress doesn't allow you to do sponsored posts on your blog to earn from it.The point is that when you create a blog on wordpress,the next step is getting your own hosting and shift to it.How on earth are you going to get the money to do that if you can't do paid posts?If you have a blogger blog, you can earn form AdSense and paid posts and get a domain to increase your paid post payout.Later,you can even get your own hosting and shift to wordpress.org,the best blogging platform possible.
WP.org is definitely better than Blogger but if I talk about free blogging platforms,I feel that Blogger is a better choice than WordPress for those who wish to go further than a free hosted blog on a sub-domain(not that I look down upon such blogs).