SDLMAME has a built in GUI now that runs when you start the app without any parameters. Although not glamorous it works well.
No need to mess with terminal to make starting SDLMAME work.
Just use AppleScript Editor and make a application with a single line like this:
do shell script "cd /Applications/mame0150-64bit; ./mame64"
Now you can just double click that icon to start MAME.