How to compare 2 point clouds ?

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### My Question

Hi, I want to compare two point-clouds using the open3d library. My main goal is to do comparison between a point cloud of an object from a LiDAR scan device and another point cloud from the 3D CAD model of the same object. But for now, I'm doing comparison between point clouds of 2 similar cars to start with.

I want to know how I should compare both point clouds to get regions of similarity or dissimilarity. ChatGPT suggested to extract feature descriptors using FPFH method. But I don't know what to do next with them.

The point to note is, both point clouds will have different number of points.