Whichever CoH Edition you choose, the Mac client is freely downloadable from your account. Actually, I believe you can even set up an account without an initial purchase beyond the first month's service (someone correct me if I'm wrong) and then download the game client.
But then you'd have to pay separately for the "expansion packs" the packages come with:
The Architect Edition specifically gives you a few additional bonuses with your new account: One month of free game time, and one of two "upgrade packs", either the Cyborg Pack or Magic Pack. Since the monthly fee is $14.99, and the pack is $9.99 separately, you're getting a $4 discount by purchasing Architect Edition.
Good vs. Evil has different items: Jump pack, Pocket D teleport power, and hero and villain costume pieces. Again, at a $4 discount, since that pack is available separately for $9.99 too.
Also, if you purchase the physical box of Architect, it'll save you quite a bit of client download time. The downloadable CoH client doesn't contain most of the game files - they download after installation via the patcher.