All SLAM solutions, and there are many good ones, are limited by the information they receive. It is possible to run host-based SLAM using our D400 series depth cameras – ideally the D435i, however these cameras are optimized for depth accuracy at the expense of field of view – D400 cannot see as much of the world as T265. As such, a SLAM solution based on the information from a single D400 camera will get lost in certain situations when T265 will not. Furthermore, the T265 is optimized for power and latency using its embedded VPU. For these reasons, T265 will succeed in many use cases where D400 based SLAM will fail.
Additionally, when using the T265, no additional resources are required on the platform in terms of compute to perform the SLAM algorithms, which means that tracking with T265 is platform independent, has a low integration cost, and can run on very low compute devices. For some use cases, SLAM on the D435i will be ideal, but for the highest quality tracking, choose the T265. For both quality depth and tracking, use the D415 and the T265 in parallel.
https://www.intelrealsense.com/tracking-camera-t265/