The breathability of gore-tex and similar membranes depends on two things: (1) the amount of water vapor inside the breathable jacket; and the (2) temperature differential between the inside and the outside of the jacket.

No. 2 isn't intuitive, but basically the greater the temperature differential, the more water vapor will be transported from the warmer to the colder area. Since the temp inside the jacket will always be close to body temperature, the only real variable is the outside temperature, with vapor transport being much more effective in colder weather.

This is why gore-tex was adopted first and most enthusiastically by mountaineers - they tended to be in below freezing weather and not engaging in cardio, so gore-tex worked extremely well. (Lower atmospheric pressure at higher elevations may have helped with evaporation, too.).

This is also why people using goretex while running/biking/hiking in 70 degree weather were not impressed - not only is there not much of a temperature differential, but cardio in warm weather while wearing a jacket will produce too much water vapor for the fabric to handle.

I generally think that a rain cape is the best wet weather gear for biking - a huge amount of ventilation and complete waterproofness above. Not good if you want to get "aero," though.