In Starcraft 2's single player campaign, two new research options unlock for every 5 Zerg/Protoss research points recovered, up to the maximum of 25 research points per race.
What are the pros and cons of the choices available at each tier for Zerg and Protoss research? Are there particular combinations that work particularly well together?
Best Answer
Zerg:
Tier 1: 150 life on bunkers is MUCH better than the shrike turret. more hits b4 it goes down, starts repairing itself at half health so at 75 hp earlier, especially with increased SCV repair speed. Shrike turret is ground only and has crappy damage.
Tier 2:The fortress is much better than the perdition turret. The perdition turret isn't better than a bunker with 4 marines and a firebat, gets destroyed often, and costs precious gas which you need for units and upgrades. The fortress upgrade is only really good in a few scenario's but packs a decent punch, is repairable, and adds hp's to your building, allowing you to use it as a wall to slow down enemy advancement, including on the last map.
Tier 3: Neither hercules nor predator unit are really required in any mission. Normal drop ships will work fine and even heal nearby units, despite the incredible amount of units a hercules can travel it requires a special building to be built and you won't have your first one until you have spent hundreds of minerals and gas. The predator unit is very decent when combined with regenerative biosteel and science vessels, especially in scenarios with many waves of enemies. This is actually a matter of personal taste as far as I'm concerned.
Tier 4: Regenerative Bio-Steel. The mana upgrades and starting energy increase are very useful in many scenarios but in the end the regenerative bio steel will allow you to sweep any map on any difficulty with more ease than normally. Also, in call of the void your battle-cruisers wont even get hurt by the rift generators.
Tier 5: The zerg slower is many times better than the control tower. Although the control tower is manually targeted and can demolish enemy waves by controlling an ultralisk in that wave, and when properly used can even be used to build a second army with separate food supply, in the end the slower allows you to move down any zerg units with them doing little or no damage to your base, even on brutal. Slow zerg are dead zerg (don't forget to use marauder slow combined with it to make the zerg sluggishly slow.
Protoss:
Tier 1: Ultra-Capacitors 5% attack speed can matter a lot on marines in a bunker. The best reason to take attacks however is if you have marauders with slowing aoe upgrade. more units slowed with marauders, more dps, and they are in a bunker anyway most of the time.
Tier 2: take the 25% gas mining. Being able to produce earlier in the scenario can save you troops to help with the next waves, and cumulatively save you a lot of hassle. Gas is often the limiting factor in the speed of your army construction. If you plan the supplies right and micro manage just a bit more orbital supply depots hardly speed up your production capabilities or game-play in comparison.
Tier 3: building 8 scv's in queue with 2 per time will rocket-launch your economy. On average a scenario will have 2-4 active gas mines in use at any time depending on your expansiveness and playing speed. those 6-12 scv's in food, combined with the advantage of not needing a command center don't weigh up against the increased production speed which will rocket-launch your campaign economy output in EVERY scenario, right from the start… If you need food later, you can always shoot your own SCV's.
Tier 4: Science Vessel vs raven is again a matter of taste, like the tier 3 Zerg upgrade. Ravens when properly micro managed can cause havoc with their damage abilities and work wonders against air units. However, if you like auto healing your tanks or anything mechanical, irradiating large groups of enemies and forming virtually indestructible death squads with neosteel battle-cruisers, I'd definitely advise the science vessels. They are my personal favorite.
Tier 5: The tech reactor is greatly superior to the orbital marine units. Although orbital drops can be useful in multiple scenarios, don't forget that with tech reactor you need only 1 of each building in any scenario, saving you at least between 500-1200 minerals and gas in most scenarios and allowing a speedy build of high tech units.
Final note:
Don't forget marauders slowing AoE upgrade in the armory. I finished the entire brutal campaign and all campaign achievements without that but it made things unnecessarily hard. Slow enemies are usually dead enemies before they even reach your base.