What
@MrsFlynn said above. Avoid Macs with Intel Iris graphics cards. Always choose NVIDIA or AMD.
And don't try an Apple laptop to play the Sims 3. You'll burn your laptop. They don't have adequate cooling and they're too weak for games like this anyway. As much as I like Apple products (I play on a Mac, even though it's on a Windows partition), they're easily exposed to overheating.
I'd rather suggest something similar to my own iMac. Cheaper if you buy it refurbished. It's great with the Sims 3, but if ever you want to play with plenty of expansions and / or custom content, it's important to
setup a Windows partition with Bootcamp to play in good conditions. But you can easily play just the base game or a reduced number of EPs without Bootcamp.
http://www.apple.com/shop/product/FE087LL/A/refurbished-215-inch-imac-29ghz-quad-core-Intel-Core-i5