I understand your POV, the frame rate difference is definitely not "vast," however, at this performance level, even a small difference can mean one more setting that doesn't have to be lowered. Seventy vs one hundred FPS might more properly be called "vast," but in actual play I probably wouldn't notice a difference.
This summary comment perhaps best illustrates my point: "The GeForce GTX 650 Ti Boost allows you to play at high settings at 1080p in today's games, whereas the Radeon HD 7790 allows you to play at medium settings at 1080p in today's games." To me, that's pretty vast (even though I've said myself that medium looks pretty good in today's games).