The memory selling company that goes under the well-known name of Corsair has made an interesting PDF document in which they explain why 4GB of memory is better than 2GB. This comes from Corsair, a company that is actually living off the sales of its memory, but nevertheless this document does cover some interesting facts.
On these full 13 pages of this PDF document called "gaming performance analysis - 4GB vs 2GB," Corsair explains about memory usage with 32 and 64-bit operating systems, tests the task switching and most importantly, the games. To be precise, Corsair decided to try Company of Heroes, Crysis and Flight Sim X.
Yet another interesting part is the testbed choice, as Corsair decided to go for Asus' ROG P965 motherboard. The rest of the specs includes Intel Core 2 Extreme QX9650, 320MB Geforce 8800GTS and 512MB 8800GT and 2/4GB of Corsair XMS2 memory.
In the conclusion, Corsair states that 4GB has become an essential choice for gamers. We like to say, not just gamers, with the Vista OS, 2GB is something that you must have and 4GB is something that 2GB were on the good old XP. As the price of the DDR2 memory is so low, getting 4GB of memory wouldn't be a costly option.
You can check out Corsair's test report here.