I don't think it matters tbh, the AMD cards need to be better to regain some market share. Nvidia are so far ahead (In terms of market share). Even if AMD cards are better performance / cost. Nvidia can afford to lose a fair chunk of market share to avoid being a monopoly and follow up with a big launch in Q1/Q2 2016. They have made a fortune on Maxwell already. Allow AMD to catchup a bit then make a big play with Pascal next year on a more mature HBM type memory architecture and die shrink. Nvdia will bring the big guns with Pascal.
It's down to AMD to deliver with the 3XX series and play catchup. I expect them to lead in performance this year and Nvidia to overtake again next year. It's always been this way though, one slightly ahead of the other and vise / versa. Only difference is this time Nvidia almost own the market (76%) and can afford to let AMD play catchup while they reap record profits.
AMD need to come out fighting for sure. I'll prob buy 390X on day one, I like to do my bit