Shut down or sleep?

I don't think Apple has ever published any guidance on that. To have any informed opinion, someone would have to conduct a study with multiple Macs over the lifetime of the product.

My Mini runs continuously, only sleeping the display. Currently, I am running an M1 mini, but had a 2012 mini running continuously its entire lifetime. It is now hosting a webcam on my 3D printer, still running continuously.

My MacBook Pro only sleeps. The only time I ever restart is when an update requires it.

If you are encrypting your Mac because the data is so sensitive others cannot be allowed access, you should shut down as it is theoretically possible to access the decryption key if it is still powered on.

I sleep my Mac

Old habits still here.

Shut down and end of day

Personal preference

I always shut down if I will be away from my computer for more than about an hour. What is the purpose of having it sleep if you will not be using it?

What is the purpose of having it sleep if you will not be using it?

A server.

With a MacBook Air, that's not likely.