Let's cover these two types of WordPress sites together because the individual goals for each are often very similar (although their designs may still be a bit different). In short, a video blog is one where the author mainly publishes videos, instead of traditional text-based posts. A photo blog, on the other hand, is essentially the same thing, the only difference being it revolves around photos.
Now, why would you even bother with a customized setup for a video blog or a photo blog in the first place when you can just use a standard WordPress installation with a traditional blogging-optimized theme? Well, to be honest here, you can indeed go with a standard setup, and your video/photo blog will be just about fine. But with some additional work (not much) put into building something that's tailor-made for multimedia blogs, your site can...