Subframe cons.... well I guess ground clearance might be a 1/2" less when your going 4x4ing, ummm, maby if you like the feeling of riding in the middle of a gaint leaf spring subframes wouldn't be for you, but come on... there are nothing.
I have the MM Full lengths. They are 100% great, but not the easiest to install, your average muffler welder might be a little overwhelmed, but common sence should be all you need.