It lets you choose the forums that you are most interested in. Say you have 5 that you care about the most, it puts them right there by hitting multiview. Then if you want new posts you can still hit that after you went through the most important to you. If you just hit new posts, it gives you new posts for the entire site. Including things that are of no interest to you with a site that is very busy like this one, it can cause you to miss something.Why do you need all the threads from your favorite forums.
I would rather just have the ones with new posts so that is what I choose.