WordPress, please! I actually asked on Twitter yesterday why people would choose Blogger over WP out of genuine curiosity. It seems like such a no brainer to me, as WP has much better functionality than that of Blogger. Not to mention it's easier to comment on a WP-powered blog than a Blogger one!
Blogger is better in the sense that it provides you a "DEDICATED QUALITY" hosting for free. WordPress blogs don't perform well on a shared host. If you can afford a dedicated or VPS hosting, then WordPress is more powerful, otherwise Blogger is best.