Never. Those same limbs hitting a climbing stick or stand is going to be 10x as loud. I hunted with a quiet fleece badlands pack for years, then the "loud" cordura Tethrd pack. I can't tell any difference. Maybe Im close minded, but there's no way I can be convinced a stick brushing across my pack is gunna be the difference maker on a still hunt over the sound of crunching leaves, sticks breaking, me growling over getting stung again by a rogue sapling etc.
I don’t use climbing sticks or a stand. I typically don’t growl over getting stung unless it’s by a bee and I try not to break any sticks.
Like I said it’s low on my priority list and all of my packs are cordura but, if I can get the exact same functionality out of two packs and ones quieter than the other. I’m choosing the quieter pack.
A couple years ago I was walking into a stand one afternoon when I saw two does feediing along the edge of an old logging road. They were about 50 yards out. I stalked to within 25 yds when I had to squeeze between two overhanging limbs. My fleece clothing went through with no noise but those does absolutely heard the limbs rubbing my pack even though I tried to be extremely slow. If I shot a compound they would have been dead but, with my stick bow I wanted to get sub 20 yds.
Is it typically a difference maker for me? No, but pack noise saved one of those does lives. Assuming I wouldn’t have missed.