As said above already: I am not a steel expert at all, I am honestly certain you and many here know a lot more than I do in that regard.
But I was actually saying that compared to REX 45 BD1N would feel more different than 4V.
And that´s definitely true in my use:
As far as I can tell REX 45 and 4V have roughly the same edge holding and are both really tough in my use.
Still not too hard to sharpen.
BD1N on the other hand is not only "not too hard to sharpen" but a dream in in how extremely easy and quick it sharpens up.
It also has decent edge holding, but nothing like 4V and REX 45.
So looking at it through my layman "coarse matrix": A BD1N Manix 2 LW will be "more different" to my REX 45 Manix than a 4V Manix.