I think we're in agreement, just looking at things from different directions.
You forgot to compensate for MPPT efficiency, they usually lose at least 3% in conversion. So there's another little bit in favor of PWM. Which might be offset by running MPPT with panels in series. Which might be compensated by the reduction due to shade on even a single panel.
But, IMHO, all this talk of electrical efficiency is moot, especially when all the itty bits add up to minor percentages. What really matters to most people is economic efficiency. And PWM generally gives you more bang for your buck until you get into a range with more power than most RV systems. I think we agree on that.
Although the cost of MPPT controllers has come down, it seems the cost/W of panels has come down faster, so I don't see that changing in the near term.
And that was my original point - for about the same cost and effort as upgrading to MPPT, the OP can put another panel on the roof and get at least twice the return on investment.
