I think this is less an issue of "facts" and "evidence" than of opinions and personal preference. Everyone will have different priorities and desires from their clothing choices.
I tend to look at BP'ing with a similar philosophy to how I do my job. A wind shirt and a rain shell are tools. To accomplish a given task (in this case a hike, with the concerns of weight, comfort, and safety), I have a "menu" of tools and techniques that I can choose from to accomplish the task.
At 2.7 ounces, I always take my wind jacket on day hikes, and the rain shell as well. I see no reason not to when my pack weight is already below 10 lbs total.
For me, I have yet to find any material for a rain shell that breathes sufficiently to hike in for any distance without using the zippers and openings for ventilation. Others may have had a different experience. Mine current choice was made for cycling and is nylon, cheap ($13.99), very light at 5.6 oz, cinches around the face and waist, and doesn't wet out after many hours in constant rain. The problem is that it doesn't breathe well at all, but has a 1/4 zip at the neck for airflow. Not ideal, but light, reliable, and keeps the rain out. The wind jacket does breathe nicely and is much preferred if the weather allows for it. But that being said, I often don't bring the wind jacket on longer multi-day hikes where weight is more of an issue. In the end, I can make do without the wind jacket, but its much more difficult to make do without the rain jacket when it starts to come down.