Phoenix and tremor: If you don't know the exact reason you're building it, don't build it.
Inferno: If the game is stalemating and you see legitimate targets, consider building these. The real decisions are whether to build the silo, and where to build it. The inferno themselves are pretty reliable and can be semi-spammed to disrupt opponent's economy. Eos tends to be better at securing value directly.
Catapult: Is how to win a team game where the map is choked up. Has enormous potential to break anything smaller than a bantha.
Firewalker: Is an extremely powerful unit that hard-counters all skirmishers, provides artillery pressure, and denies areas. Great unit.
Hammer: Is cheapest artillery in the game (other than defender :P). Use them to punish aggressive forward porc earlier than most people are ready for. Do not spam, they are not a replacement for rockos, and good players will punish spam every time.
Racketeer: Great unit. Use to disrupt opponent's plans and composition. Scales well, by denying prime firing space (the front row). I find it has finicky micro/ai, but haven't seem anyone else complain.
Impaler/pillager: Standard artillery. If you can protect it and keep it firing at valuable targets, they generate advantage very quickly.
Crabe: Highly efficient at killing pretty much everything that's cheaper than it assuming proper positioning and support. Does not do well against things that are more expensive than it. I like to make them if I'm planning on going strider to hold off aggression.
Pene: Great unit. Sort of the opposite of crabe, in that they're weak against cheaper units, but great against everything that's expensive. Can snipe commanders, stingers, striders efficiently.
Wolverine: Useless in small numbers, polarising in high numbers. Lots of weaker players make these because they can spamstomp games, but when wolverines are countered, they lose so hard it's often gg (firewalker, wyvern, phoenix etc.).
Saturation vs. direct shot doesn't seem like a particularly useful dichotomy, especially the way you've labeled them. Phoenix for example, while providing a decent spread, is kind of a precision weapon in that you need to deliver to a very precise place. Compare to tremor, which says "get out of this area plz I will give you all the time you need".