I was just wondering if it betters to just lock the threads that are needed to be locked or should we just get rid of them by deleting them because they take up space and we can't post in them?

It actually depends, I think. IF the topic is pointless, such as a dupe of another, it should be deleted, rather than closed, while if there is some lesson to be learned, like a topic about KO's or something similar, the topic shouldn't be deleted, just locked, so that people can see what is not right to post.