Difference in the R9 280x

So I am thinking of adding an R9 280x to my 7970. I've been seeing online that there are revisions, such as the Gigabyte r9 280x Rev 1 and the Gigabyte r9 280x Rev2.

From what i can see the Rev 1 uses two 8 pins and the Rev2 uses an 8 pin and a 6 pin to power it. 

Is there a reliability or performance difference?

im guessing its just them binning for better power efficiency thought it mostly wouldn't make a huge difference anyways.

$40 is the difference ... 

which would be better spent on a R9 290 with another $20

Gigabyte Radeon R9 290 4GB WINDFORCE 

http://pcpartpicker.com/part/gigabyte-video-card-gvr929oc4gd

They are pretty much (literally) the same, i hear you have to watch out with non-blower designs in xfire. Should, perform well.