Bottom line - I think there are other factors to consider.
My $.02, having towed four different trailers around the country.....
My heaviest, largest and least aerodynamic trailer tows the best. It tows so great that I don't use WD or sway control. See my sig below.
My personal theory is that there's probably an equation that describes the relationship between weight, physical dimensions/shape, and stability. My lightest trailer was my least favorite to tow - that was 28' and 5000 lbs. I think it was too much of a sail and not enough weight.
