Knowing both is not hard. Also if you don't change too much defaults it's not hard to downgrade to vanilla programs. My init.el is above 3000 lines, but I can easily use vanilla Emacs any time if I need to (or vi/vim/ex/ed for that matter). Same for bash, my .profile and .bashrc combined count ~300 lines, both POSIX compatible, and I'd hardly have a hard time at a foreign shell prompt. That's because I use configuration to extend, configure and personalise a program, instead of trying to recreate it.
