I see ~15W avg between the two (780 vs 290). Not too big of a worry, really. Especially when you can get a
290 for $318.40AR shipped.
Hmm, the reviews I saw showed the difference at ~60 watts.
Regardless, I pulled the trigger on the 780 6gb this morning. It was about a 25% premium on the AMD290, which I'm ok with. I've had both brands in the past and while I don't have any solid complaints about the AMD's, NVidia does seem to have them beat in energy and therefore heat; and I just seem to like the Nvidia ecosystem better.
I did read this review yesterday:
http://www.hardocp.com/article/2014/06/11/asus_strix_gtx_780_oc_6gb_review_exclusive#.U8AAlJUg9es
That suggested that there was a benefit to having the 6gb.
So, I figured I'd rather spend the few bucks now knowing that I'm likely buying way more than necessary at the moment and have the Vram "just in case" as opposed to sitting there in two years wishing I'd spent a little extra now. Running a pair in SLI was an excellent point for this card that I hadn't thought about.
This is my first time buying such a high end card so it's a little bit of an experiment. I'm hoping that it will remain usable for a little longer than my traditional practice of picking a mid-range card and getting impatient with it after two years.
As an additional bonus; it's an EVGA so if an 880 does pop up in the next 90 days I can just utilise the step-up program and jump onto that bus!
Thanks for all the help and comments everyone! It arrives on Monday via Amazon so it'll be a long wait over the weekend.