That's not all completely true. It is true that After Effects is much stronger with most motion graphics tasks, but smoke's masking/roto abilities, plus the sheer speed of the system make After Effects look like a turtle on even the fastest systems. smoke has much more extensive math operations abilities than After Effects. Not only that, but you can integrate true 3D geometry into your smoke compositions whereas the closest thing in After Effects fakes it by importing some geometry, and then turning it into a flat layer. Once you learn how to work with smoke's DVE in conjunction with some good sparks you can do almost anything you can do in After Effects with a lot more interactivity, especially at HD and film resolutions. It's not quite as flexible as AE however, and will require a bit more planning when putting together shots.