laugh
I found your question interesting because I have experimented with various things in that regard. I can't say one thing fits all, but lately I carry Frogs Toggs in anything but winter months or when the forecast is for rain. I love my 5.4 ounce Marmot wind jacket that full zips down the front. It resists rain surprisingly well for 15 or 20 minutes. I carry it for another layer in many conditions. But if it likely to rain (I'm in the Pacific Northwest and hike all year long) I take one of my several full zip Gortex-like jackets with pit zips and plenty of room under for insulation in case I'm benighted. (and equivalent rain pants or lighter).
I have a lovely anorak my brother-in-law gave me that is waterproof and light weight, but in truth the Marmot is a better wind jacket and the Frog Togg top is just as light and is less clammy because it opens up. I picture the Frog Toggs as 100% waterproof and the anorak as 95% wp. It has a light coating of PU on the inside and DWR finish on the outside.
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Jim M