Lenovo is shipping computers preinstalled with man-in-the-middle adware called Superfish. It's a web proxy that can hijack any web session, including encrypted/https sessions. And since the root certificate is the same for everyone with private key present on the machine that's now publicly
Since much of the time will be spent running emulators, RAM is important. All 2015 MBPs come with 16GB of RAM that should handle most of what you throw at it and be enough for the next couple of years.
Android Studio has the best out of the box experience on OSX. Linux suffers from lack of resources (compared to other platforms) due to it not being as popular of a dev platform for Android development and Windows has some Unix/Windows mismatches.