I tried a rain cape briefly in the Seagull century. Hooking my thumbs through the loops was clumsy and I found it hard to operate the controls. I had to be very careful not to snag the arebar elbow pads. The cape billowed in the headwind effectively becoming an air brake. The back flapped up and got hung on my backpack.
I'd say thumbs down on cape. My winter jacket is water repellant and has worked in light precipitation. I also have a $10 performance rain jacket that works fine in cold weather.