The difference between the idiomatic uses of these expressions may be illustrated thus:
The complications of this case are such as will take some time to unravel.
The complications of this case are such that they will take some time to unravel or such that it will take some time to unravel them.
Such as may legitimately be treated as a pronoun-preposition: we may write "I would not do it for such as him" and need not insist pedantically on "I would not do it for such as he (is) ".