Well for "Doom 3 and UT2004", system 2 will probably get my vote. My new system I am building will have 1GB 2xDDR400 also obviously. But, u have the opportunity to check it explicitly in less than 20 minutes
.. That's why I pointed out "how" and when the 3xDDR333 might actually be superior.
If whatever application you are running requires a lot of RAM, it will have to hit the HDD. That will slow ur system down quite a lot. Take it from me. I run a lot of signal processing apps on my computer. And I usually reach a threshold where the system bogs down "very noticeably" (and I mean drastically!). I am sure Doom 3 and UT4 is not as intensive as in this respect, but it's still good to be aware of such issues. Having "faster" memory but less of it is not always better.
But, your question has to do with Doom 3 and UT2004 and not Signal processing applications
. While system 2 is most likely (99% sure) is the better system for these applcations, you can easily verify if this is true. Takes very little effort. And it'll give you the actual numbers. That's why I said, what I said..