For the Karve I have 3 Plates a D and E Solid Bar and an E Open Comb. I only just got the Dart so it is very Early Days.
For the Karve the OC plate definitely has a bit more Blade Feel but I would say in terms of efficiency the 2 Es are about the Same, the D is smoother and in fact if I bought it again I would be inclined to swap the E Solid Bar for a C in Either OC or Solid Bar.
The Karve is pretty forgiving on blade angle but is smoother with a slightly steeper angle, My initial impression with the Dart is that you have a narrower window and it certainly seems to like a steep angle but hit that spot and what a shave.
My impression of them both is that they both give a great shave, but neither is a brain out razor, you have to concentrate a bit. I have a Game Changer 0.84 and that to me is more forgiving you have to really mess up to get a bad shave from it.
That said I love my Karve and being brass it feels warm and soft to the touch , the Dart to me is a very pretty razor and I personally love the machined finish. They are both staying
Guess that's not very helpful with you decision as I like them both !