Okey, we're getting there. I have come up with a bit of a flu so the fan fic may be deleyed a few days. Anyway...
Although beam weapons could severely pound the shields of an ISD, we need to know the shields strength. Shivan Tech differs from SW tech, meaning that SW shield strength could differ greatly from FS2 tech
Also, the hull of an ISD is supposed to be made up of some kind of advanced Durasteel or some other kind of powerfull alloy. SW episode 3 opening scene, we see a destroyed piece of a seperatist cruiser being blown into a Venator. The piece only makes a small scorched mark. However, freespace ships get holes blown in them just when a fighter crashes into it. You can see fire and/or smoke steaming out of the damaged area when they take damage.
Resources needed to create Terran ships mostly came from Earth, meaning either they are mostly made of Titanium are some other powerfull Earth alloy. SW metal is not native to the Sol system meaning it could be far stronger. Say, an ISD's shields are brought down, the beams still need to penetrate the hull. That video of an ISD v.s. an orion is not entirely accurate. Weapons and shielding are probably not the same as they are in the SW universe. I believe the person who made that vid is on this forum. He said that the ISD was not as good as the ones for future SW mods, so now doupt that vid is irrelivent to this debate.
In SW EAW, missiles or other weapons which do not utilize laser technology can bypass shields. Would flak cannons have a similar effect? Or can missiles be blocked by shields too?
Chances are, SW ships are more susseptable to beam cannons due to their more advanced shielding technology and metal alloys. However, Terran shielding tech was reverse engineered from Shivan tech, so who knows how long Shivans have been able to evolve their technology.