Whats difference in ddr2 dual channel memory and regular ddr2 memory which one is better memory for speed?

There is no difference in the memory - both are dual channel capable, but need to be installed in pairs to utilize dual-channel architecture of a motherboard.

Your mobo must have dual channel capabilities to support the memory. See Hardwaresecrets.com, and click on the Memory heading at the top. Scroll down to DDR memory, and check the other sub-titles.

dual channel is better