I've used various "breathable" jackets over the years, including proper goretex stuff, of varying budgets, and have found that none of them breathe fast enough when I start doing anything physical. While they may mean I am drier on the inside than if I was wearing a non breathable jacket, and while I am drier than if I was not wearing a water proof, I'm still not dry. I've recently been investigating Paramo as my next jacket option. I've chatted to a few people, including some MRT team members who wear Paramo on duty, and the closest I've heard to a negative is that it can be warm in summer. One MRT member said to me:
I wear @ParamoClothing for all my hill activities & work. Most of us do. Gave up membranes years ago.
Said MRT member is a hydrologist by day and spends most of his working life on a hillside or moor in all weathers. One of the selling points that is appealing is that you can get panels of the jacket replaced if you want to. Having trashed jackets in the past due to bike accidents, being able to have the sleeve replaced for a reasonable fee appeals a lot more than getting a new 80-150 quid jacket every 1-2 years, when a non repairable cut has appeared, or a motorist has taken it upon themselves to pull out in front of me...
As for the gram counting. Yes the best place to lose weight is round the waist, there is a lot to be said for taking weight off the back too. If you can shed a kg or two you can dramatically reduce the stress on your body. Something many bushcrafters do by way of the "light weight philosophy", often without realising it, is not taking non essential kit. I'm willing to bet that those of you in wool and ventile, when you go for a multiday hike, about the only thing in your pack that you don't use is the first aid kit (and if you are unlucky, you use that too...). Weight saving comes not just from the gear you take, but also from the gear you leave behind.
Julia