I don't believe for a moment that any crimped joint is "gas tight". And I don't believe a crimped large cable is ever better than solder, even though I agree that good crimped lugs make fine battery cables.
If you think crimps make better battery cables, the issue may be with your soldering skill on large lugs. It is a different animal than small electronics soldering that we all learned in middle school. Different tools required. I do not claim to be good at it, but solder slugs make me look good at it.
However you do your battery cables, find good heatshrink with adhesive on the ID.
