I have a Dell Inspiron 17r (N7010) laptop with 3GB of RAM (DDR3-1333 PC3-10600), running Win 7 x64. The RAM is 2 modules; 1 x 2GB and 1 x 1GB.
Should I upgrade the 1GB module to 2GB or 4GB? Will there be a noticeable gain in performance with 6GB over 4GB? I don't do video editing, but I do usually have a lot of programs open at the same time. According to Windows Task Manager, my typical physical memory usage is 70% or more
Also, I keep seeing something mentioned about matched pairs. Will 4GB perform better than 6GB since then there will be 2 x 2GB, as opposed to 1 x 2GB and 1 x 4GB?
Also, does it matter if I buy Crucial memory, or is it better to buy OEM memory from Dell?
When people say matched pairs (as in "dual-channel"), they mean two sticks of RAM that are of the same exact type. In your case, it probably just makes more sense to go for the 4GB module. You *might* get slightly better memory PERFORMANCE with the 4GB, but the extra physical capacity in 6GB greatly outweighs that.
You can buy from Crucial, but OEM might be cheaper anyway. It doesn't make that much of a difference, as long as you get a module that is DDR3-1333 PC3-10600.
If you want more memory with better performance, you might consider just going for it and getting a 2x4GB pack. Obviously it's your choice though.