The honest truth is that, non of them is better than the other. Yes, wordpress can be user friendly than blogger in most cases but it is not better in SEO than blogger, as much as blogger is not better than wordpress SEO-wise. Or even traffic-wise.
So I conclude this by saying, non is better than the other in terms of traffic and SEO. They're both content management systems (CMS), you're the one who has to make the CMS SEO friendly, non of them come SEO ready. If they came built-in with SEO ready features then you wouldn't need plugins for instance or even an SEO friendly theme/design for that matter.
Hope that makes sense, not only to you but to everyone else who think wordpress is better than blogspot.