Stack vs individual unit fire

[Steelwhip]

so...something thats recently cropped up in my thinking process. Is there any difference in having whole stacks firing at targets or having individual units fire separately.

does firing large stacks generate the same casualties and fatigue to a target or is it better to fire individual units separately. Im talking in a general overall average sense. 

the thought process got kick started when I was playing ME '67 doing the '73 golan heights scenario (stick to the plan) and that the Syrians (and to a large scale I suppose the computer player in general) would fire these huge stacks of units individually and it seemed to me...that in a long term engagement-my units were taking a ton of fatigue damage from it. I would toss a fresh unit into the fray and a couple turns later they were looking at 200+ fatigue.

now granted this may have been from the Syrians were operating in battalions and the Israelis were operating in platoons and companies, and there was just HUGE stacks of syrians (serious..I think at one point there was a stack of 12+ syrian units in one hex!)

so whats the advantages/disadvantages of firing stacks vs firing individual units.