Simms all the way.
I have a pair of Headwaters that I have BEAT UP for about 50 days a year for going on 7 years. I had a pin hole leak that I felt that was starting this spring and I dropped them off in Bozeman on a trip, and 10 days later they sent me back my waders completely cleaned, all the seams re-taped and a few other pin holes/wears in the gore-tex were fixed. All for no charge, not even shipping. And they are performing like new again.
I was hoping they'd tell me the were shot so I could upgrade to a new pair of G3's but no such luck. For now, I'll keep on beating the crap out of these.
That said, the only other wader I would even remotely consider would be the Patagonia Rio Gallegos.