SEO or a writer's point of view:
On every single aspect, ranging from templates to SEO friendliness, wordpress is miles ahead of blogger. However if you are an analytic freak and addicted to Google Analytics then should choose Blogger for wordpress.com never allows Analytics to be added and instead offers a far less powerful inbuilt tool.
Developer's point of view
If you are developing a wordpress CMS for your website then I will recommend avoiding it as wordpress is easily hacked and you need to take all possible steps and ensure you have backups, in case if your website gets hacked.