I was considering a poncho, but opted for a lightweight rain jacket and cycling rain pants from Decathlon instead. Been caught a few times and the combo works really well. Keeping your hands dry is a different challenge 😅

I have a J&G rain cape. It is really great - thumb loops means you have a little dry cabin (protip: if you have a spot on your handlebars to hook the loops, it keeps your arms dryer). Yes, if you are going fast it does have a little resistance. BUT, it also breaths much much better than any rain jacket I've ever had. So you don't get nearly as clammy or sweaty. To me, that's a worthwhile tradeoff.

I don't think a poncho would work very well in regards to air resistance, it would act like a parachute. I bought a thin, neon green cycling jacket from MEC (Canadian REI) that works really well. I still need rain pants though.

Curious about this too. I have one of those giant flappy things that only keeps you dry in a gentle sprinkle, ie where I am located, always soaking wet.

Definitely one with thumb loops. I also add a belt to pull in around the waist if it's windy.