The actual kill capability, supression, penetration, etc is an eldritch calculation based on the
"...complex interaction of weapon class, HE Kill, and Warhead Size..." plus a small random factor.
Two weapons of the same warhead size, weapon class, HEK, etc "should" produce similar results but change any one of these factors and results will vary.
If you want to supress (or kill) something grab the weapon with the highest HEK AND highest Warhead size you can find - the 600mm Karl Morser ticks ALL the right boxes, lol! 