When available, dual-channel is always better. Basically, hrm, what's the easiest way to explain ...
Your CPU is very, very fast. The channel it uses to talk to the RAM is slow by comparison. Any tricks the motherboard can use are helpful; dual-channel architecture is such a trick. It accesses pairs of RAM as, well, two channels instead of one.
I'm having a hard time putting this simply. Here's a primer on how dual-channel works. Trust the wiki, not the lemur.
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