Someone told me that "anywayS" is good to use only when you talk to your close friends, etc. That is, VERY informal. That said, when you are looking for a Russian equivalent you have to decide whether to keep this stylistic feature in Russian or drop it (and possibly notify us as to which one you prefer ).
Both "в любом случае" and "так или иначе" are pretty much formal cliches. Informal things like that are "на хрен", "блин", "бля"(obsc), "вообще" or even "ваще" (phonetical contraction like "gonna" or "whatcha").

- Да кто он ваще такой?!
- Кем он там себя возомнил на хрен!
...
- В любом случае/так или иначе, это случилось бы.
(I see it best with pure "anyway", not anyways) and I incline to use the formal versions, accordingly. They are interchangeable, I guess, so it's no matter which one to use. Well, maybe случае...случилось бы - sounds a bit rough so I'd personally use "так или иначе".