There has been a question raised by Yuga at Yugatech.com regarding the difference of Blogspot blog and WordPress.com blog, and here is my take
Blogspot Blog use different programming command compared to WordPress.com, You have the freedom to alter the design of Blogspot that will suite your taste. In fact there are lots of free theme for Blogspot that you can readily use. while in WordPress.com you will not be allowed to alter the design unless you are going to pay them, I think it is US$ 10.
Can I migrate from WordPress.com to Blogspot and vise versa? Based on experience it is easy to migrate from blogspot.com to WordPress.com rather than WordPress.com to Blogspot.com. Since WordPress.com has a one press button to extract all your post and comments from your blogspot blogs.
Search Engine Index
Yuga agrees that Blogspot.com is easier to be index by Google rather than WordPress.com and it is also my experience thru my other blogspot blog.
Both of them uses widget in customizing the layout and links in your front page , So I may say that both of them is ok in that matter.
In viewer participation WordPress.com is better since Blogspot just recently changes on how they handle their comment. You cannot comment with your self hosted URL in Blogspot not unless you will put your url inside your comments.
One of the most important factor in SEO is the Sitemap, But neither blogspot nor wordpress.com could provide you one. Not unless you will built it manually, this is one of the reason why you should opt to use the self hosted blogs.
Do I use both?
Yes I use WordPress.com ( here ) for my personal blog and General Blog. and I use Blogspot as well in monetizing my niche blogs ( here and here ) and I can say that the Blogspot blog is more optimized rather than wordpress.com. You can also see my other blogspot blog below at my footer.
Can I use automated blogging software in both ?
Yes you can, In fact I am using Windows Live Writer in posting on all of my blogs, So it can interface with all.
Can I use Plug-in in both
Plug-in is a terminology use for WordPress, WordPress.com has it’s ready to use plugin in their system and you cannot alter these plug-in at all. In blogger you can have some similar plug-in but in a different way, Usually it is being provided by a group of programmer that do some customization for Blogspot. You can find some thru Hoctro for some Blogger Beta Hacks.
There are also other platform that you could use in order to have your blog, You can also use multiply and others there are also some site that offer free hosting if you qualify with their requirements and there are also some site that gives you a low price for blog hosting. Believe me, If I knew this things before I should have started all my blogs in hosted rather than doing it in the free site. That’s is why I have it now. And if there is a chance to have another niche blog I would again purchase another domain and hosting. Believe me, It is easier to monetize on self hosted blog. You also have full control over it.
But if you insist on having free blog, My suggestion is take Blogspot and take wordpress.com if you just want to blog. But believe me later on you will like to monetize 🙂 .