The biggest advantage is that you get more information through
the result of a skill roll. Under the old SLA system you only knew
if a task failed or succeeded. Now, through the result of the Success
Die, you also know how good or bad it succeeded/failed.
In combat, the amount of damage a character causes is directly
related to his attack roll. In the old system, if you succeed you
always deal the same amount of damage. You now also have a detailed,
but quick to apply, system of locating where somebody is hit; with
semi, burst or autofire, you can now follow the "path of bullets",
creating a realistic portrait of where autofire bursts hit (an not
a random arm, arm, leg, head, torso hit pattern). The melee system
allows now for real "dice duels" of attack, parry or dodge.
Through the Success Die, this system easily allows supplemental
skill use. If you are in a situation where one skill can have an
impact upon a second skill (like first analyzing a security system,
then trying to disarm it), the success/failure of the first test
has an immediate effect upon the difficulty of the second test (by
adding/subtracting the result of the Success Die of the first test
to the target number of the second test).