EX Explosive, which is not regular explosive, does +2 DV and -1 AP. The armor calculation is DV VS Armor, so any + to DV also pushes the damage into physical. In this case, the difference is a net 3 for EX Explosive versus a net 4 for APDS. The explosive ultimately does more damage, however, because on an average, -4 ap will prevent 1.333 damage soak. Thus, the damage difference is 7 to 4.
For EX Explosive versus APDS, you are trading off having one extra point of armor pent ration for an average extra real damage box.
Again, I am talking about hardened armor. Body armor is not exactly what shaped charged and sabots are made for...
Okay, I'm doing the math.
Because of the automatic successes from hardened armor, which is modified by AP, EX Explosive is slightly worse than APDS. Specifically, EX does an average of .5 less real boxes of damage and it needs one more success or DV to deal damage through hardened than APDS.
Against all other targets, EX Explosive is the superior choice.
The core rulebook says under Explosive ammo that "these slugs carry shaped-charge explosives, designed to explode and fragment on impact." That means they are applying the shaped charge in a way other than to penetrate armor. Also, sabots are just sleeves that allow you to fire a round smaller than the bore diamater. Armor Piercing Discarding Sabots are something in the nature of hard metal darts made to fire out your gun.
And also, we are talking about pistol and rifle ammunition, not dedicated anti-vehicle weapons, which is likely where you are applying those terms from. Antitank rockets apply shaped charges in an entirely different way.