THey are both even i have found. If you expect your blog to take off, and eventually get a domain for it, then you might want to start with wordpress, as you can then easily migrate over to a wordpress site. If you want no hassle, and just want to publish then choose blogger, there is a very limited number of bells and whistles there.
Have a look at your niche and see what other people are doing, and if there is any type or style of layouts you like.
you can search health blogs blogspot.com / wordpress.com to check them out