I'm not a big gear guy but this is one area I follow pretty closely as I encounter brush and briars pretty much anywhere I hunt and up until about 10 years ago the options just flat sucked as the initial run on performance hunting clothes was dominated by the westies.
Patagonia Field Pants - These are by far the best overall outdoor pants where you may encounter briars I've owned. The upper is incredibly stretchy and comfortable, and the cordura armor is brushed in a way that it way more flexible and quiet than most cordura type fabric. It's not louder or stiffer than a pair of good blue jeans. I have three pairs that should last me a decade or two. But they stopped making them, unfortunately. I can still find odd sizes now and again but keep looking for my size every month or two and haven't found any lately. I don't do much gear evangelizing, but these pants I do. Wish someone would pick the exact design back up.
First lite Sawbuck is okayish. I bought the first run so maybe things have changed, but their upper material isn't stretchy enough and the cordura is more typical cordura, it's a tad loud and stiff. It's better than your run of the mill cotton bird pant, but it's a little loud for archery deer usage.
Kuiu came out with brush pants, I have not yet tried them. They look appealing, if I didn't love my Patagonia's so much I'd undoubtedly own a pair.
Orvis also makes some similar synthetic/performance-oriented brush pants, have not tried them either.
I have a bin full of run of the mill cotton brush pants. Pass on those. You want a synthetic upper with a light cordura facing.
I have several other pairs of synthetic pants with tighter weaves that I would call more brush resistant than your typical male yoga pants that pass for hiking pants, but none of them really stand up to mf rose, greenbriar, or heavy blackberry canes.
