You also have to consider the temperature of the rain. Warm summer rain is very hard to deal with, the humidity inside a breathable waterproof is matched by outside and you get very hot and clammy.
Cool rain is easier to deal with.
On my North Sea circuit I took 2 waterproofs, a well ventilated summer Gortex that worked OK in light rain, and a heavier duty winter-weight Paramo for the cooler northern sections (also doubled as evening jacket). Paramo was always more comfortable to wear but may be too warm for summer touring. It is also bulky to carry.