I never had the chance to use one in a live game but if we are talking about turrets placed inside ship interiors, i would probably go for beam+pulse to have a turret with minimals size and instagib potential. Not sure how much damage per tick a 1 block beam + 1 block pulse turret would do but I can imagine its enough to kill an astronaut in one or two ticks. Only downside would be the reload of course in case of more than 1 intruder.
E:
On second thought that may not work though because the turret does not check for line of sight and would shoot even though the target is behind cover. I guess damage pulses would be more suited for instagib "turrets".