623B into OTG is for more damage and circuit.
214A Airthrow is for better mixups.
Both are standard, and which one you should use depends on what's more important at the time, as well as your own taste/ability.
Jumpcancelling 214A on block strips its ability to be jumpcancelled until after your next combo. As such, there are often situations where 214A cannot combo into Airthrow. It can be a bit distracting to keep track of, so many players tend to skip the 214A to make sure.
However, there is no reason not to use it after landing consecutive combos on the opponent. The first combo will always reset this ability, so if the subsequent mixup connects then it's pretty obvious that 214A Airthrow will work.