I use sandisk extreme (45 MB/sec) in my D600 and am finding them fine.
Your type of photography will influence your decision. If you're a sports shooter, for example, you'll make constant use of continuous shooting, so want to empty the buffer as quickly as possible. If this is the case, I'd recommend the 90mb cards. Would also recommend the faster cards if you shoot high resolution video.
If not, then the 45mb/s card are more than adequate.
My experience (with D600 and now with D800) is that the 45mb/s is fast enough.
95mb/s is only a slightly faster. The difference is very small. If you shoot long burst it'll only give you approx. 4 extra frames (e.g like 32 instead of 28) before the buffer fills and the framerate drops.
Your type of photography will influence your decision. If you're a sports shooter, for example, you'll make constant use of continuous shooting, so want to empty the buffer as quickly as possible. If this is the case, I'd recommend the 90mb cards. Would also recommend the faster cards if you shoot high resolution video.
If not, then the 45mb/s card are more than adequate.
even in continuous shutter mode of 12 frames per second