It really is a matter of preference, I think that's how it's always going to be.
I think the problem is people are still thinking of QAC only in terms of a consistent technique like waveshining where it's a matter of memorization. That's fine, it can certainly be used like that and is much easier to use that way. In that case b-sticking might not be a great benefit. But I still think QAC has more potential (although maybe not!), specifically as a means of movement and maybe in other ways as well. In this case, it's sort of like an intense version of wavedashing, since QAC Dashing is not only much harder to pull off in the first place, but also requires a great deal more precision with the angles. And since it's a form of movement, it requires you to react consistantly and for long periods of time based very highly on how your opponent freely moves. As I said, it's the same reason people used c-stick to smash in melee. Pulling of one frame smashes is easy, and pulling them off consistently takes practice but is certainly doable. However, an argument can be made that using analog + A will never be as consistent as the c-stick with smashing.
As for DI, it's possible though difficult to do whichever attack you'd like and DI in the direction you'd like as well.
For me personally, I don't DI and attack in different directions nearly as often as I QAC, and in any case have started practicing attacking and DIing in different directions without the c-stick and am getting better with it. And I've never felt like I needed a c-stick to smash, since I don't often spam smashes one after the other consistency isn't as important, I don't use them as often as QAC now, and a whiffed smash isnt as bad as a result for me as a whiffed up-b QA (even the whiff isnt as bad with a b-stick, it's usually a jump rather then lag).
P.S. By no means am I bad at up-bing my QAC. Even though earlier in this thread I said it'd be impossible to QAC Dash without the b-stick, I figured out how to do it anyways (after being owned by raptor, lol). Even still, to me the difference between using b-stick and up-b is still there.