When I was a range officer for my department, we taught a different grip to the officers armed with revolvers than we did those armed with semi-autos. While the grip taught was different for revolvers and semi-autos, our preferred stance for each group was a two hand hold with the arms fully extended. We also taught one handed shooting skills. Even here, there was a difference in use depending on the distance of the attacker. You didn’t want to use the same technique at grappling range as you would at long range. In addition you would not use the same grip on a rifle or shotgun as on a handgun. The same is true in regards to knives. Different tools usually require different techniques to be used most effectively.