Hi, I work in this field professionally - you are correct up until the tradeoffs. It is not the case that the spatial resolution is higher - in fact, semiconductor manufacturers have struggled to get ToF sensors much above VGA in mobile form factors. In general, ToF systems have a considerably lower maximum precision than structured light of the same resolution, especially at close range - typically structured light systems have quadratic error with range, but the blessing that that curse gives you is that at close ranges, precision goes up superlinearly with horizontal resolution. This is one reason that essentially all industrial 3D scanning is based on structured light. The other is multipath inference, which is specific to time of flight systems (and you can see the effects if you look at a ToF’s results near a corner - the exact corner itself will be correct, but the walls immediately adjacent to it will be pushed out away from the camera).
Temporal resolution is more debatable, because ToF is a lot more conducive to “extremely short, extremely bright flash” than structured light is. But for example, there are systems that run structured light (specifically, single-shot dot pattern structured light, like that seen in TrueDepth or Kinect), or its two-camera equivalent (active stereo) at exposure times of 1ms or less. It is all about the optics stack and sensitivity of the camera. So I don’t agree that temporal resolution is a compelling advantage either.
The main advantages of ToF are that it can be built in a single module (vs two for structured light), it does not require significant calibration in the field when the device is dropped or otherwise deformed, and it is easier to recover depth with decent edge quality. In general the software investment required for a good quality depth map is lower, though in this case Apple has been chewing on this for many years. Another potential advantage is outdoor performance at range - while historically this has been a significant weakness for ToFs, more modern ToFs adopted techniques to improve this, such as deeper pixel wells, brighter and shorter duration exposures, and built-in ambient light compensation. These are hard to do with structured light without manufacturing your own custom camera module. Finally - and I suspect this is why Apple ultimately picked it for their rear depth solution - because time of flight is a single module, it can be worked into the camera region on the rear of the device without having to have a separate opening for the illuminator and camera. The quadratic drop in accuracy with range that I mentioned above can be offset not just by resolution but by the distance between camera and illuminator - for a rear mounted device, the temptation is to make that baseline large, but this would put another hole in the back on the other side of the camera bump. I don’t see Apple going for that.
Temporal resolution is more debatable, because ToF is a lot more conducive to “extremely short, extremely bright flash” than structured light is. But for example, there are systems that run structured light (specifically, single-shot dot pattern structured light, like that seen in TrueDepth or Kinect), or its two-camera equivalent (active stereo) at exposure times of 1ms or less. It is all about the optics stack and sensitivity of the camera. So I don’t agree that temporal resolution is a compelling advantage either.
The main advantages of ToF are that it can be built in a single module (vs two for structured light), it does not require significant calibration in the field when the device is dropped or otherwise deformed, and it is easier to recover depth with decent edge quality. In general the software investment required for a good quality depth map is lower, though in this case Apple has been chewing on this for many years. Another potential advantage is outdoor performance at range - while historically this has been a significant weakness for ToFs, more modern ToFs adopted techniques to improve this, such as deeper pixel wells, brighter and shorter duration exposures, and built-in ambient light compensation. These are hard to do with structured light without manufacturing your own custom camera module. Finally - and I suspect this is why Apple ultimately picked it for their rear depth solution - because time of flight is a single module, it can be worked into the camera region on the rear of the device without having to have a separate opening for the illuminator and camera. The quadratic drop in accuracy with range that I mentioned above can be offset not just by resolution but by the distance between camera and illuminator - for a rear mounted device, the temptation is to make that baseline large, but this would put another hole in the back on the other side of the camera bump. I don’t see Apple going for that.