And 5' seems like it would fulfill the need of giving some room to maneuver while keeping the entanglement hazards to a minimum. So what would the advantage of a 7' hose over a 5' hose be for the average non-tech diver?
If you're a very big built person the 5ft MAY be a little tight to use (as its routed under the right arm). Most people its fine but some large shoulder/chest people could possibly find it a bit tight. Other than that i cant think of any real reason.
7ft is designed so people can exit a wreck or cave in single file - if that isnt an issue then really 5ft is fine.