> But I always felt that it SC2 was more successful in taking out APM and "Deathball" mechanics

On "Deathballs", no. SC2 always allowed the player to select all military. SC2 always had smoother patching and better programmed "flocking" behavior.

In SC:BW, it's an APM feat to simply control 12 Dragoons/Goliaths/Siege Tanks across a bridge. Meanwhile, a hundred SC2 Stalkers can easily chain-blink across the same terrain no issues.

In SC:BW, the bad patching and bumping is part of the balance. In SC2, all units moved too smoothly and too easily, as such deathballs are always easier to setup.

SC2 allowed players to easily control Deathballs, so then they tried to balance that by making splash attacks more powerful.

In contrast, it's literally impossible to control a deathballs in SC:BW, because you can only ever select 12 units. Literally impossible to control more units (and even then, those 12 units were extremely wonky around bridges or other terrain features).

In SC:BW, the deathballs debate is innately moot. No human can control a deathballs anyway so it's not even a debate. Like controlling 48 zerglings is a feat reserved for top pros.

Further, because control of 48 zerglings is so hard, pros who COULD do it use the 4x groups of Zerglings on increasingly divergent points of the map (harassing multiple bases), rather than concentrating their efforts in one area. Might as well "tax the opponents APM" by attacking multiple locations if you have such good unit control or APM.