Theoretically they're both the same in terms of SEO. Some people believe that Google favour Blogger because its their own product... but I don't think there's any solid evidence of this.
Yep it's a common misconception and it's not true. Whichever works best for you will depend on the type of site you have and want to run. Your site will only be as good as you make it and Google don't give people extra merit just for using their blogging platform... no matter what anyone says!