For most applications you won't notice a difference between the two provided the density is the same, meaning 2X2gbddr2 and 2X2gb ddr3. Video editing like higher banwidth/faster ram especially when your running a speedy hard drive.
The prices of ddr2 and ddr3 isn't dramatically different right now. If you can grab some ddr3 for close to the same price go for it. Another benefit to ddr3 is the ability to use it in a future upgrade, you don't have that option with ddr2.