The default and recommended setting is to leave the purple screen of death up to help you notice that het host has died and also leave the PSOD up to help troubleshoot the issue because on reboot you can loose your logs.
What to do:
Login via ssh to ESXi server
Execute command:
esxcfg-advcfg -s 30 /Misc/BlueScreenTimeout
where 30 - the number if seconds you want to wait until reboot.