Help figuring out which Mac to buy and still play Sims 3

I haven't played The Sims in years, back when Sims 2 was still releasing new content. But now I want to be able to play the Sims 3 and I need some help in figuring out what computer to buy. I want to stick to a Mac, because that is what I am used to. I've tried looking around the forums here and reading other threads but I haven't found the answers I'm looking for so I hope someone here can help me.

This is the specs for the computer I was looking at getting.

MacBook Pro
13.3-inch (diagonal) Retina display; 2560-by-1600 resolution at 227 pixels per inch

8GB of 1866MHz LPDDR3 onboard memory

128GB PCIe-based flash storage
Intel Iris Graphics 6100

I've read that there are problems with the Intel Iris Graphics though that makes the game nearly impossible to run. So I also looked at these specs for a MacBook Air

4GB of 1600MHz LPDDR3 onboard memory

128GB PCIe-based flash storage

Intel HD Graphics 6000

I've differing things about the game running well on a MacBook Air. Would the Sims 3 still run well on this, even though it has only 4gb of memory, versus 8gb?

Are either of these computers a viable option to play TS3? Should I just forget about about it and look into TS4 instead? I really want to play TS3 since it sounds like a much more detailed game.