I had a bunch of Cooper's PET bottles that I used with my 1st couple batches while I gathered glass pop tops. They're 740mL,or 25.16ozs with screw on caps. Get the caps really tight,& they work just fine. It takes 30 of them for a 23L,6.072USG batch. they get hard as they carb up. I was told on the Cooper's forums by their head brew tech that they have a nylon lining & are good for about 8 months max.
So glass bottles are def better in the long term. But for average gravity beers & how long they really last,they're fine.