Installing and Uninstalling
OS X: Drag app out of .dmg to install, drag it to trash to uninstall.
Linux: Synaptic Package Manager helps to simplify Linux package installation, but is still harder to use; an alternate way to install software is with the Add/Remove Software option.
Mac OS X
OS X: Double-click on it.
Linux: Either double-click on it or run a command from Alt+F2.
Legacy Application Support
OS X: Intel OS X doesn't support PPC OS 9 apps.
Linux: Runs any Linux app, no matter how old.
OS X: Comes with Safari, a tabbed browser.
Linux: Comes with FireFox, a tabbed browser; it's extendable and customizable.
OS X: Simple, not too much too it. Has a junk filter.
Linux: Simple, has PIM. No junk filter.
OS X: AIM and .Mac
Linux: Most known IM services.
OS X: Easier to use.
Linux: Definitions are not as good.
OS X: The terminal comes with more developer commands, and Xcode comes on the install DVD.
Linux: Some developer tools in terminal; may need to install restricted software or build-essential
OS X: 3 , Linux: 3