In the end the concept that you will be inconsistent is unavoidable. If you choose the rolling method, you will grab ledge at different times depending on how you time your b inputs, making you regrab early or late and changing when you would let go of ledge optimally. The thing is that while, yes, the rolling method gives different timings, so does the shine method. If you were completely consistent with the rolling method you would grab ledge the same timing. If you are completely consistent with shine method you will grab at the same time, but that is also near impossible. How many frames you leave between the ledge release, shine, dj, and up-b are also going to be inconsistent. You won't get the perfect frames every time.
I prefer the rolling method because it allows me to react, where as the shine method really doesn't. If I'm drifting a frame or two away I can visually see it easier and try to adjust my timing. It's not perfect by any means but there is no actual perfect method. Just practice it a ton.