Personally I'd like to see gun physics so that my gun doesn't clip through walls. Its sometimes really annoying when my gun fails to function because a small amount of it is in a nearby piece of clutter. I think making the gun move rather than fail to fire would be a better way of handling it. This sort of a system has never annoyed me in boneworks or H3 and I think it could go a long way to improving immersion.
However, I don't see one having a distinct advantage over the other so I think maybe having both would be good and leave it to be toggled. Its preference at the end of the day, I'd prefer where my guns collide rather than not function but I know some people don't like the idea of the guns bumping into things.