Hello,
In my opinion if the system foresees it for ESXi installation I would use what DELL calls "BOSS" card, or the equivalent (functionally speaking) marketed by other vendors with different names, I mean, I prefer to keep the operating system installation separate because I think it helps to avoid hassles in case of problems and give more freedom of action. USB "boot" devices (or whatever we want to call them)? After some unpleasant experiences, I haven't taken them into consideration for a long time.
Surely other users will be able to bring you their equally valid considerations or suggestions.
Regards,
Ferdinando