Performance will really depend on what sort of hardware you’re running on. With the right hardware, Motion is hard to beat for this sort of thing due to its realtime capabilities.
AE has a much broader toolset, especially with plug-ins, and a larger user base (which means a lot more support resources for now).
Mac-based pros will have both in their toolboxes.
Jim Kanter,
Digital Film Institute
http://www.dfilminst.com