re "Then you probably have AGM batteries (or you SHOULD!)" -- why? They cost 2x, last maybe 1.5x, still need proper battery compartment. I mean, they are nice but I can't see pushing it too far.
re: "the old Pulse Width Modulation (PWM) style. It surely has it's limitations" -- the advantage of MPPT is not that much for small installations (under 500 watts) like you'll find in an RV.
What is important in either a converter or a solar charge controller is good charging smarts coupled with a maintenance mode that will inhibit battery sulfation during periods of minimal use. Examples of these would be the ChargeWizard based converters or the BatteryMINDer charge controller.