Blogspot or Blogger and WordPress are two most popular blogging platforms that are free and you can use both these platforms on your own domain. In case of Blogspot you can attact your domain name, using Domain Mapping facility that Blogger platform provides, in case of WordPress, you can install WordPress manually or directly as it comes free with many hosting panels. In case of hosting WordPress, you have to pay for the Hosting Plan. In case of Blogspot/Blogger it is free of cost.
But, Blogspot which is owned by Google, has certain community guidelines, and post adult/explicit content is against their guidelines, so sooner or later, they will remove you blog and you will lose all your content. You worked very hard, you wrote very good articles, they will all be gone, if you use Blogspot, you will not even get a warning or anything, just Bam!!!
WordPress is more powerful and complicated platform than Blogspot, it gives you a lot of freedom, and from the SEOs point of view, WordPress is far better than Blogspot. And because you are hosting your own blog you will never lose your content, no third party can remove your content. In case of Blogspot, Google can anytime remove your Blog, and all your hard work will go wasted.
So, always prefer WordPress over Blogspot/Blogger. Blogspot is a good platform but they way Google controls it, is bad for anyone who uses it.