Self-proclaimed NERFED king
Actually, considering how it worked in DPPt, a normal capture has a x^4 chance of working, while a critical one would have a x^2 chance.As far as I understand, a critical capture has roughly twice the chance of succeeding.
The way it works is this:
A standard catch checks 4 times - 3 shakes and stars.
A critical catch checks twice - 1 shake and stars.
Thus, a critical capture has about twice the chance of success.