I like to install demo data and replace. because it shows you where everything is by default.
When you first install WordPress, it comes with a sample page and a sample post. Usually that’s enough to get a feel for how things will look. I don’t know of any theme which comes with its own demo data. There are plugins that you can use to create demo data; I use Demo Data Creator on a couple of my test sites, but you have to be careful if you use it on a production site. The option for deleting the posts & pages will delete ALL posts & pages, not just the ones created by the plugin, so its best to delete them one-by-one, which can be tedious if you have a lot. But the plugin is really good at not only creating demo posts & pages, but comments, categories, and users.
