A confession: at the (very) beginning of my walking career I bought a poncho. Main reasons were: I didn’t have much money, it would also cover my big backpack, provide enough ventilation to not get sweaty, and combined with gaiters keep my legs dry.
This is what I hoped.
Well, I only used it for one holiday. I got terribly wet as the wind made the whole thing flap madly. I also couldn’t see where I was putting my feet. Not good on uneven terrain.
The waterproof jacket-trousers-pack cover combo is much better!
(Other systems are available)