As per common sense goes, there should not be any difference between free and paid blogs as far as traffic is concerned. As we can see, people read a blog that meets their queries. As far as the platform is capable of providing authentic information, good entertainment or whatever the blog is all about, there is no reason, that viewers would not visit your page.
On the other hand, if you are practically asking about the earning on the basis of numerical calculation, even then, going for a free blog is obviously beneficial. If you have to shell out money before you even start earning, that is a loss in every sense and where is the point? But if you start with a free blog, create a fan following of your own, be successful in getting an AdSense Approval, it would be profitable from every sense.
Once you establish a blog with a decent traffic, you can upgrade to a paid one in no time and then it would be really worth it.
But the true foundation of good earning would always ask for fresh content and if you need to hire writers, you need to pay them at times. a paid blog would become a burden if you are unable to fill your blog regularly with fresh content.
Thus for a beginner, a free blog would always be the most recommendable platform.