Thankfully there is an eye comparison thread on DoA, but since you I know you don't really do DoA, I'll post some of those reference photos here.
12mm:
12 vs 14:
14mm:
14 vs 16:
16mm:
16 vs 18:
18mm:
I believe that should pretty much over it all. And if you change your mind about being on DoA, just let me know.
A hobby isn't supposed to leave you wistful, regretful and vaguely disappointed. BJD collecting is as customizable as the dolls themselves. Do whatever pleases you the most, because otherwise, why do it at all? All for the 'Gram Bitches love the
'Gram.