I still remember (1970's) when set screw fittings, die cast or steel, were understood for indoor use and compression fittings were for outdoor use. We used to say "set screw or raintight fittings". Egineers require compression fittings in almost all specifications, so the term raintight is no longer used. Nevertheless, the installer is the one who makes sure the fitting is tight, whether set screw or compression. I agree that steel fittings are stronger, but they can rust. I've noticed that our electricians complain a lot about how the compression fittings are easy to strip out and the constant loss of the interior compression rings take up time to find and/or replace. You can almost always find a screw to replace a missing set screw. My biggest complaint with using compression fittings is when the helper leaves out our can't find the interior compression ring, but still installs the fittings. No visual inspection will spot this.