The SI-abilities are all situational, although ones like SI-Invincibility, Defence, Dodge, Evasion and Distraction are good for avoiding big hits.
SI-stun allows for a free swap when it works (which should be most of the time), giving you a free hit against slow opponents.
SI-wound allows you damage an opponent even if it has armour, shields or distracting moves, and can be timed to coincide with a non-damaging move like instant-distraction. It also makes it beneficial to save it’s possessor for later even if it’s low on health, since it can allow you to save a sweeper from a sticky situation and still do damage after it’s possessor is KO’d.
SI-Slow can allow you to stop a fast sweeper in its tracks, potentially ruining a setup and allowing you to get a free hit in. Even if the dino being swapped in is low on health, it’s a good setup for a revenge kill, allowing you to setup your own sweeper or tank.
SI-Nullification is admittedly not that great, and I don’t have much experience using it anyway. It can ruin a setup, but it’s risky.
SI-Ferocity can occasionally come in handy if your opponent is low on health and has used up it’s big-hitting moves, allowing you to sneak in a counterattack and take it out regardless of its speed.
The non-damaging (directly anyway) SIs can mean the difference between victory and loss, and should definitely not be underestimated.