i think it might be that with the Vee style blade, right in the crotch of the V can get a tiny kink on the blade edge, then its not much good after that, iv seen this happen before.
This Ventum one looks like it might have best of both idea, the outer flange presses the line in against the blade. im guessing they are bigger than first appears, almost like a knife size, not a key ring size. So your cutting with a safe knife, and the lines jammed into the opening which looks wide enough to take depower, webbing or whatever you hack at.
looks like this style has been adopted by scuba. seems pretty legit