It's a well-known fact the Lam-intosh is made for losers. 
One of Microsoft's next tv-advertising should be like this: a group of mentally-handicapped people going around to shop for a computer system. Eventually they'll find a computer that best suits them, a Macintosh. Then the slogan catch-phrase appears on screen, "Winners don't use the macintosh" ! That ad would surely be effective. 
C'mon now, that's not nice!
How about we just go about explaining it this way:
Think of the Extensions folder on your Mac as the Startup-Squence on your Miggy...it just needs to be altered as text (like any old OS...yeah, this shit is old).
The other folder you mention that starts stuff after boot (dunno what it's called in OS X....even though I own three Macs...LOL), just consider it to be the WBStartup folder on your Amiga.
Has this already been mentioned? Ah, I don't care........I'm drunk!

PZ.