See, this is the kind of thing I mean when I worry that people are misjudging the type of goalkeeper Henderson is.
Is Henderson quicker to sweep off his line than De Gea? Obviously, though De Gea has actually improved quite a bit in that regard this season. Is Henderson generally a very good sweeper? Probably not. During his Sheffield United season he was bang on average for the league statistically and I haven't seen him do much this season in that regard beyond what you'd expect an average keeper to do.
So if the argument is that we're better able to play a high-line because Henderson is a better sweeper than De Gea, that's fine. But if people get it into their head that Henderson is quick to sweep by general standards or that he'll be our equivalent of an Ederson/Alison then they'll be disappointed once they stop having De Gea to compare him to.
I have such a clear image in my head of Henderson ousting De Gea, everyone celebrating that we now have a commanding, pro-active, "modern" goalkeeper, only to slowly realise that by the league's general standards he's average in those regards and also relies a lot on his shot stopping to stand out.