If your opponent has a "longer weapon", you are going to have to close on them and get "inside" their reach (like a boxers clinch).
Have fun with that.
The kerambit is limited to seratta/hubud range, where it would be great for trapping and slashing strikes against an unarmed opponent. So is a good folder.
A knife fight is an assassination gone wrong. If I have to face off against someone else with a blade, I'm going to keep them at largo mano range until I can get an opening or a good enough pass for a stab. None of the kerambits I've seen are suitable for stabbing.
I think if there are anymore technical discussions along these lines, this thread will be diverted to prac-tac.