The SR300 is suited to scanning small objects, whilst the R200 is suited to scanning larger objects and the full length of the human body.
However, the R200 is older technology than the SR300 and is no longer supported in the current and future RealSense SDK software (though support continues in the open-source Librealsense SDK). If you want a combination of the latest camera technology and the advantages of the R200, a good choice for you may be the new ZR300 camera. It can currently be pre-ordered from the Intel online store for shipping in mid April.
You can click on the information tabs in the store listing for the camera's specifications, and also read its data sheet document.
You may also be interested in an article from 2015 on using RealSense to measure shoe sizes.