What's the differences between suppressor, punisher, and defiler upgrades ??
Suppressor commanders deal 2x the amount of circumstantial damage as their basic action counterparts, and about 1.25x more trauma damage. Like all other enhanced commanders, they are unaffected by chosen tactics.
Defiler commanders deal 1.5x circumstantial and 1.25x trauma damage, compared to a defiler surround action. This does not include the various 2x damage multipliers that a chosen may be subjected to during a defiler surround action. This commander upgrade allows the commander to perform a T2 break, if they reach Lv.3 in the applicable circumstantial damage.
Punisher commanders deal damage differently than any other source - meaning they don't follow the standard 1,1/2,1/4,1/8 step down damage pattern as most other sources do. So, I'm just going to share the baseline damage. Keep in mind, Suppressors deal 100,75,50,25 and 200 damage (trauma/circumstance). Punisher commanders deal 1000,300,100,30 and 3000 damage. So they deal about 20x a baseline surround damage in terms of trauma to their primary, but only a bit more than 2x to their weakest. They also deal 15x damage to their target circumstance damage. Then, the commanders total damage is multiplied by the punisher efficiency. (so, 10x if 1000%) Of course, punishers are the inferior way to break T4 vulnerabilities, compared to using a Punisher forsaken.
Additionally, demon commanders can combined multiple upgrades into a single unit, barring some restrictions. Punishers can only be combined with both a Defiler and a Suppressor (Completion, 60EE), Punishers with a single Suppressor (Synthesis, 10EE), and when no other upgrades are added, two punishers can be combined together (Versatility, 5EE). Doing so combines the damage output of each added upgrade type. And, as mentioned, this is before the punisher multiple is applied.
As for strategy? I haven't really cracked the code on when to use a suppressor upgrade, or how to use a defiler to reliably break a chosens T2 vulnerability. How I tend to use a demon commander, is to load them up with a punisher, and maybe a suppressor, give them 3 captures and just enough turns to keep my inital target chosen occupied until their reinforcements arrive, and use the time in between to build up bonus damage via the Reality Sealing upgrade. Alternatively, a 2-turn 5 capture completed commander does wonders for hitting the chosen where it hurts during the final battle. guaranteed to get high trauma Lv's without breaking a T2 by accident.