Seems like all it does is take up memory instead of writing over what needs to be written over(I'm not a computer savvy person so I don't know if this makes sense).
I think you are confusing memory with the space on your hard drive. Anything stored in memory (or RAM) is volatile. E.g. everything is deleted from your RAM when you turn off your computer. In contrast, anything stored on your hard drive is usually stored there until, say, you delete it. In the case of updates from Microsoft these would be patches to the Windows operating system. Therefore these updates (or patches) would cause the system to take up more hard drive space not memory.
Based on the aforementioned, is it more memory you want to add or a bigger hard drive?
That said, you should always keep the Operating System (i.e. Windows) fully patched. As technonymous said, as new security "holes" are discovered all the time. Not applying Windows updates will leave your system vulnerable.
Edited by Agouti, 12 November 2014 - 03:30 PM.