I think a martin and a gibson should be in ones stable, but both should be mahogany dreads. That is the foundation and then you build from there.
With respect to guitars cutting through in a bluegrass jam... I'm by far no expert, but the only time I heard a guitar measure up to the banjos, mandolins and fiddles was watching Randy Scruggs and his aj, and even then when it goes from banjo to the guitar - the lead takes a step back. Give your ears a second to adjust and he's just plain awesome, but as good as the guitar is, it does not project as well. Maybe it's mic placement.