Is it better to have 4GB RAM in dual channel or 6GB as single channel?
Solution 1:
One thing to consider is the Operating System. Are you using a 64-bit operating system that will recognize greater than 4GB of memory? If not, just stick with the 4GB in dual-channel mode.
Also, if you are going to be running some very memory/harddrive intense programs (Such as running a database), I would go with the 6GB configuration (Assuming your OS is 64-bit).
If you plan on gaming with the machine, I would go with the 4GB in dual-channel mode primarily because games rarely take advantage of any memory greater than 4GB. Once you hit the 4GB mark on memory, speed is the factor.
-Brandon
Solution 2:
This greatly depends on your use. If you never plan to have massive applications open or many large applications the Dual Channel is far better. But if your going to hit the top of that 4GB limit you should stick with the greater capacity.
Most of your limit is not going to come from RAM anyway. Typically its HDD speed that slows RAM loading UNLESS your are planning on using programs with a lot of calculations.
Summery:
Big programs more Ram=better
Fewer small programs or high calculation programs: faster RAM=better.
Solution 3:
I'd recommend that you experiment with both.
Some motherboards use triple channel configuration and some can use dual channel for some modules and let other modules work outside dual channel, so there won't be any performance difference.
Another option which you may consider is to buy 2 more GiBs of RAM and use 8 GiB in dual channel mode. This way, yoo won't have to upgrade RAM for some time. Also RAM modules which are part of kits are often available for separate purchase, so you probably won't have any compatibility problems.