I’m with everyone else who prefers to have their critters at home rather than alone and unattended. Most pets will have an easier recovery if in their familiar environment rather than the sterile confines of a vet practice.
The SOP I’ve experienced for routine spaying has always been bring them early for the surgery, and pick them up at the end of the day. I am given instructions for care as well as information on who to call if I suspect something is NQR.
That being said, it’s ME who stays up all night monitoring “just in case”, while my beloved is comfortably sleeping…
I see no point in leaving an animal overnight if there is no one there for observation.