On two occasions, I have had Platypus Big Zip containers develop leaks, usually along one of the folds. Interestingly, I have never had a standard Platy 1 or 2 liter water "bottle" develop a leak even with hard use. The leaky BZ's were circa 2005 and the issue may well be resolved now but I know that once upon a time they did develop leaks, easily.

For a simple water bottle I see no reason to carry a Nalgene when a recycled pop bottle is equally sturdy and a third the weight.

I use a Sawyer Squeeze, the larger version of the mini. I have had no problems with it in two years of use. And, that is with the original, failure-prone, bags.

I've never tried but I have heard that Platy threads leak with Sawyer equipment. Evernew bags do mate with Sawyer filters, or so I've been told.