Are there any advantages to buying a game on the Mac App Store (MAS) instead of Steam?

For a SteamWorks title like The Baconing, if you buy it on Steam, you get both the Windows and Mac versions.

The catch is that Steam requires you to have an Internet connection, at least periodically, to verify that you own the game.

As far as I'm aware, those are the only differences.

I was just about to ask the same question. I haven't bought any game on Steam. But from my experience with the App Store and iTunes Store, they often have discounts on big events and public holidays (Christmas, Labour Day, etc).

IMHO, SteamPlay titles sometimes cost more. yes, you get both Mac & PC version. But in my case, I only play in one platform at a time. I play the heavy games on PC, and then the more casual games on my Mac Air.