If you want a 1.2, you'll know it. For portraits, forget about it. Even if you *have* a 1.2, (And I do, for my film Canons,) you should never shoot *at* 1.2 except under very precisely-controlled conditions or when it's absolutely the only way to get the shot. Especially on crop, DOF is so wafer-thin, you just won't get sharpness on living subjects that way, not souch as you'd need to worry about the lens.
I have mine cause it focuses very easily in the field, ...most 1.2s are damn soft wide open. Exceptions are things so expensive that if you can afford it, you know exactly why.
You only use that lens speed in the field when you just can't handhold it stoped down. Even to f2 or so.
Especially under controlled conditions, choose the lens that works best where you will actually be shooting. In general, speed better than f2 should be a focus aid and a fallback. Shoot stopped down more, anyway.
My 1.2, I use to nail focus when it's otherwise hard to see, and I try to get off that wide stop if at all possible. Not a case where narrower DOF is necessariloy better. Unless you know precisely what you're about.
if you want to do portraits under controlled conditions, 1.8 will do you.
Or, if you have to ask, you don't need a 1.2. A 1.4 is often a better all-around lens, and most digital bodoes can't show you the difference anyway.