I have a pair of montane wind pants (pertex). I don't wear long pants in normal life and use these any time I need another layer, so these get a lot of use. I've had them for something like 4 years, and they've done >2000 miles of backpacking, a few miles of X-country sking and snowshoeing, snowboarding, trail running in the snow to work for an entire winter, etc. largely on-trail, but also several days of 12-foot blackberry laden bushwhacking where they were my only protection (ouch, my poor legs). They weigh about 4 ounces. After that much mileage the only damage is a hole on the thigh where I knocked my alcohol stove over on myself while lit, and melted a bit of the pants. I can't believe they aren't shredded (I'm not easy on gear).
I sweat an insane amount, so a non-breathable rain pant simply doesn't work for me in most situations. I found I never wore them after carrying them far too many miles, that's why I switched.
Recently though I discovered why waterproof pants are useful. I went snowcaving up near Tahoe. My wind-pants were completely soaked through in 9F weather (frozen when outside the cave, wet when inside), leaving only my under-armor tights to keep my legs warm. Luckily I'm used to hiking in cold weather in shorts, and otherwise had sufficient gear, so I was okay, but I don't intend to repeat that mistake.
So, for your purpose I say you won't be sorry with a pertex wind pant. If you want to be prepared for anything though (not really needed on the AT), waterproof is a must-have.