It depends on resolution, if 1080P then the 2 x GTX970 would equal or better the 980Ti but at 1440p or 4K the additional Vram on the 980Ti kicks in and it would be better. http://www.techpowerup.com/reviews/MSI/GTX_980_Ti_Gaming/30.html
thaks for information
i would go for x2 asus strix 970