Facebook is good place for promotion of any site or product. We can easily get good amount of traffic. Also we can get connected with lots of people there.
You can't stay Twitter is better or Facebook is better. There are countries where one or the other is more common. Twitter can offer you wonders, but if it's not used in that country, you can't really do much in your local language.
Try integrating Facebook and Twitter, then target people in your niche with some of tools on the market. Next, set up a Fanpage/Business page and drive your twitter users to your Fanpage. Also, put a link on your blog to your fanpage.
Facebook fan pages is really good to promoting your site.....but make sure you have more than 50000++ friends first....... Normally, my site got 1000-2000 visitor everyday just from Facebook fan pages...
I don't know why you would use your personal account to promote on Facebook... Just make another account. To echo those above, FB can be useful if you have something that people would actually enjoy. They don't share blatant advertisements.