does buying domain name differ ? what are advantages? and what are diadvantage? i know i ll lose backlinks is this true? is it better to keep it as .blogspot?
The obvious advantage is that if you want to upgrade to WordPress then all your homepage back links will still be pointing at the same place. Blogger do have a tendency to delete blogs if they don't like them. So it's a sensible idea if your Blogger blog has any dubious content.
I think for long-term success having your own domain hosted is essential. The flexibility that WP gives is worth it from a management point of view. Anyway, how many serious blogs, that make money online, do you know that are hosted in blogspot? RS.
It all depends on what you want to do with your blog in the long run... for instance, a lot of people are turned off by Blogger, let alone the dot blogspot dot com at the end. Also, most sponsors, advertisers, whatever would NOT even look at your site because of the free hosting and everything.
But you also have to remember there's a WHOLE other side of sponsors that hate free hosted sites. For instance, if you ever decide to write a paid review or whatever and go through a middleman company like payperpost, sponsoredreviews or whatever, then they will not approve you even if you have a PR or good Alexa stats...
You could do that, but wouldn't it make sense to get hosting and use Wordpress? It would be so much better.