I'm not sure either - and there's one of the problems. We're not given the full cost and consequence of each alternative.

I did read a piece a few months back discussing glass against recycled plastic. Plastic apparently needs far more washing, and at higher temperature and pressure, before it can be recycled. The washing to remove glue, labels and dried food which are all more difficult to get off plastic, and also because plastic recycling is so easy to pollute and ruin the whole batch.