From my point of veiw, a grounded Y is much safer. Working many years in very old industrial plants, if any of the ungrounded phases faults they are more likey to trip the breaker. With all the bad grounding in old machinery, it can be fun trying to find a fault. The old time electricans would always tap the machine with the back of the hand before starting to work around them. Sorry to say I'm one of them! On a 480 Y ungrounded system, I read 300 volts between two presses with shorted motor winding.
