Although I have to wonder just how much stuff you've downloaded for UT2k3 if your UT folder is 6 gigs, and what's the problem with 120 mb's more, 6 gb is really small change when compared to the 120+ gb drives out there. It's still a somewhat valid argument though, especially if your computer's more than a few years old and you don't have a larger "modern" drive. (But then again, if you *do* have an old system you probably wouldn't be able to run UTk3 or U2 in the first place...)
As for your getting tired of having the CD in the drive, there's always the zillions of No-CD patches for just about any game you have. If you actually own the game, there's no one stopping you from backing up the appropriate .exe and applying the patch to get around the CD problem. Wham, problem solved, end of story.