I have never had a rain jacket that breathed adequately. Maybe I just sweat a lot, but the only advantage a jacket has for me is that it keeps off the wind. I will be wet from inside.

A cape/poncho can be awkward to keep your thumbs in the loops, does not work real well for drop bars, requires fenders (unlike a rain suit) and a front fender flap, but it works best for me for commuting in street clothes. It breathes better because there is air flow from below, so I stay dryer.