My apologies, Dave, but you are apparently the lucky one.
I am used to spending my entire work day in my SQL GUI. My productivity is much better than using the command line and emacs mlisp bindings don't do it for me either. So please don't get into a religious war over CLI vs GUI.
I cannot ever run pgAdmin III for more than an hour on a MacBook Pro without it crashing and this damages my productivity. This has been my experience for over a year with two employers with local and remote databases (and very different network configurations). It happened on both employers' MacBooks as well as on my own MacBook. SSH tunneling on or off. It was happening on Yosemite and is no better - possibly worse - on El Capitan. If you like I can probably find a bunch of crash reports and forward them.
Can you tell us anything about your Mac configuration that might be making your setup more reliable?