It kind of depends what you're planning to do with your site. When you see a blog at /blog, it means that that website has something really cool at / which isn't a blog. An example might be the Spotify website: they have a normal web site where you can download there software and see information about pricing, and you can click blog to see spotify.com/blog.
Just to mess with your mind, the entire Spotify website actually runs of WordPress. You can use WordPress to have real pages, other than just blog posts, and you can set your blog pages to reside at a URL like /blogs so that you have a front page. You can change this setting, as and when you feel like it.
Alternatively, you can just upload your WordPress files to the /blog directory of your site, and install it there.
If you're not planning on having other pages or a front page on your site, then there is no advantage to the /blog bit. If you want other pages in front of your blog - so you want to make a page that people see when they arrive at domain.com, rather than them seeing your WordPress blog right away - then you should put your blog at /blog. To do that, you have the two options I outlined (albeit briefly) above.