Zealot - Sure, more WW damage, but you’re paying for it in cost. You can just make an extra Zealot for every 3 you make in P1.
Dragoon - Absolutely no benefit. Inexcusable, tbh.
Immortal - Sure, nice barriers with upgrade, but you have GS and you’re better off spending extra money on damage to kill the enemy faster rather than getting tankier. And you need barrier research to make it remotely worth it.
Reaver - Not running out of ammo is nice, but that’s not worth 30% more on a Reaver, which is not a cheap unit.
HT - This is a mixed bag for me. Enhanced storms with plasma surge is pretty nice. But once you merge them into archons, you really start noticing how few storms you actually get compared to P0.
Archon - See above.
Phoenix - Not particularly impressive and it sort of becomes useless to lift units when you can’t really lift a significant number of them at once.
Tempest - The enhanced ability damage is useless. If you haven’t killed the wave in the time it takes for the DOT to take effect, that probably means your own force is probably already destroyed. It’s useful for trains, but that’s about it. Not worth the 30% extra cost, which decreases the number of Tempests you field in the first place.
Overall, I think P1 is poorly executed. The cost penalty is awful. A fairer trade-off would be reduced damage on certain combat units while their abilities are buffed. This should only apply to Zealots, Immortals, Phoenixes, Tempests, HT/Archons, Reavers since those are the ones that actually have abilities to apply anything to.
20% damage penalty on these units sounds tolerable.