This is an excellent question!
Of all of the spiny plants found in Alaska, the micro barbs from Devil's Club (Oplopanax horridus) a.k.a. Alaska Ginseng is the Kryptonite of breathable waders. If you don't know this plant , be sure to look it up. It is found from Northern Coastal BC through South Central Alaska. It can be found along rivers, lakes and open shaded forest and is usually densely clustered together. Watch your hands and exposed skin!.
The Simms waders tend hold up much better than other breathable waders in the bush wack battle, but are by no means impervious. The G3 Guide Wader's legs, from mid thigh down, are reinforced 5 layer Gore-Tex. This helps them sustain abuses such as Devil's Club much better than other wader brands, especially low end models. The biggest weakness to the G3 is that it is designed to be the lightest and most breathable wader on the market. From the mid thigh up, the G3 is only three layers Gore-Tex, which is often where most of the branches of Devil's Club hang. If you can, go around the cluster, but if you must go through it, tread lightly, move slowly and you'll be good. Try to run through it like a train and you might get derailed.
The best wader for this scenario is the G4 Guide Wader. The 5 Layer reinforcement is provided from the waist down and all through the rear. This makes it a much heavier duty wader than the G3. Be forewarned, the Best of the Best may be bulletproof, but when the kryptonite comes out, the Man of Steel falls vulnerable. Moral of this story: no matter how good of a breathable wader you have, you need to move slow and carefully when dealing with plants such as Devil's Club and other spiny/thorny bushes and leave the brush busting to the bears that you scare off of the water.
Also be sure to take advantage of Simms Repair Department and send you're waders in for evaluation and repair at the end of each season. !st time is free!