There is currently little data about face tracking with the 400 Series to make a proper comparison with the well-established SR300, as most people have used the new cameras for scanning objects and environments rather that body areas up til now. So your choices include:
1. Use the Creative BlasterX Senz3D (or the Razer Stargazer, another SR300-compatible camera) with the built-in face tracking support of one of the old Windows SDKs, preferably the '2016 R2' version for optimum stability of face tracking.
2. Use the SR300 or a 400 Series camera with the RealSense SDK 2.0 in combination with a face-tracking module on another software platform such as OpenCV.
The same options apply to hand tracking.