Here are the reason why I prefer the cut out(maya 2022 and previous) :
1. it is cleaner in the sense that you don't need to have an entire body if your are just movind points in the head.
2. the file size where your keep your blendshapes will be smaller. You might not notice this is cartoony characters, but if you are working with high res geo (like in realistic character) you will feel the impact in size and loading times.
3. if the body topology changes, all your facial blendshapes are still safe. Even adding an extra loop in the fingers later on will mess up all your facial blendshapes.
4. cutting out the head will allow you to display the head with different LODs. You might get 24 fps with one char in the scene but if you have 4, i hardly see it will keep up to 24 fps. If you cut out the head you can display it with a procy
body so you will have 24 fps with many chars in the scene.
In a nutt shell I find separating the head a cleaner and more optimize design. Just do what ever you think is best for your workflow.