I think to be safer go for the smaller optic the difference is the amount of a few teaspoons, in terms of size it will probably make little to no difference that’s what the surgeon told me when I was choosing.( my size choices had a 25cc difference)
if it risks rippling I would take the advice of the surgeon – just think what would be worse : rippling or boobs that are a smidge smaller .
And on a side note to be honest most girls end up quite a bit bigger than they and their surgeon planned it’s impossible to really guess what you’ll end up. But with 420 I’m pretty certain you’ll get the look you want .I for example ended up with 28E’s although I’ve been wearing 32 D/DD’s as they’re easier to find , I only got 250 and asked for a small C cup !(granted my back measurement is small so it’s all relative of measurements) xx