I have done few ESXi installation (Boot from SAN) on HP DL380 G8/G9 Servers. During the installation Selected UEFI boot mode and installed the ESX on a SAN Datastore.
after the installation if i change Boot mode from UEFI to Legacy then few ESXi hosts are booting properly and few of the ESXi are not booting.
Will it make any difference if i change the boot mode after the installation From UEFI to Legacy or vice versa ??
Yes, it will. You don't change the boot mode once you've installed it as that impacts its ability to reliably boot up. If you're on 6.5, you probably want to use UEFI for the additional features it brings like secure boot. And even if you aren't going to use them, legacy BIOS is going away, so there's really no compelling reason to use it anymore in this day and age.