Is 2x4gb of RAM faster than a single 8gb module

Yes!

slightly, yes.

does "slightly" mean its worth spending 3-5 dollars more on the 2x4gb kit or should i buy a single 8gb module?

Yes, spend the 5 bucks and get 2x4GB sticks

Best answer selected by Lazar_99.

It is marginably faster. I usually advise using exactly two RAM sticks, for the following reasons:

1. You get dual channel. Almost no improvement at all, but since there is nothing to lose from using it, might as well do it.

2. If one stick fails, you still have a working PC. This one is a major benefit.

3. If you use more than two, there is a greater chance one of them may malfunction during the PC lifecycle, giving you all sorts of headaches.

So use 2 memory sticks with enough capacity.

you get HUGE performance gains from 2x4 if you're using an APU (personal experience from amd's apu... i don't know about intel). otherwise, it makes little difference