For lighter rain/drizzle/wet snow I prefer using a windshirt on the move over a rain jacket. It has enough water resistance (in the 300 HH range), but has many times the breathability (~20-40 cfm) of any rain jacket.
Absolutely.
The highest air permeability ratings (CFM) in a waterproof/breathable are in the
tenths (like 0.2-0.5). Something like the Patagonia Houdini is in the 4 range. Some windshirts push 40-50 cfm as mtwarden noted. It's not good or bad, it's about picking what works for a given situation. Windshirts are so useful in the western US.
