in my matchups, and I believe armor to be fairly superior in TvP when using bio due to its effect on zealots.
Numbers:
Marines:
+ Show Spoiler +
In the case of either marines without any upgrades, or marines with 55 health that use stim, your marines will have 45 health going into battle.
Zealots kill 45 HP marines with no armor in 3 hits, (8+8)x3 = 48
Zealots kill 45 HP marines with +1 armor in 4 hits, ((8-1)+(8-1))x3 = 42
A 33.3% increase
Marines with 1 attack upgrade kill zealots in 24 hits
Marines with 0 attack upgrade kill zealots in 29 hits
A 20.8% increase, much worse than the armor upgrade
Stalkers kill 45 HP marines with no armor in 6 hits, 8x6 = 48
Stalkers kill 45 HP marines with +1 armor in 7 hits, 7x6 = 42
A 16.6% increase, in this case the attack upgrade is slightly better
Marines with 1 attack upgrade kill stalkers in 25 hits
Marines with 0 attack upgrade kill stalkers in 30 hits
A 20% increase
Colossi kill 45 HP marines with no armor in 1 hit, 23x2 = 46
Colossi kill 45 marines with +1 armor in 2 hits, 22x2 = 44
A 100% increase (with 55HP marines they would take 2 hits to die anyway, however +1 armor allows you to stim the 55 HP marines and stil die in the same amount of hits)
Zealots kill 45 HP marines with no armor in 3 hits, (8+8)x3 = 48
Zealots kill 45 HP marines with +1 armor in 4 hits, ((8-1)+(8-1))x3 = 42
A 33.3% increase
Marines with 1 attack upgrade kill zealots in 24 hits
Marines with 0 attack upgrade kill zealots in 29 hits
A 20.8% increase, much worse than the armor upgrade
Stalkers kill 45 HP marines with no armor in 6 hits, 8x6 = 48
Stalkers kill 45 HP marines with +1 armor in 7 hits, 7x6 = 42
A 16.6% increase, in this case the attack upgrade is slightly better
Marines with 1 attack upgrade kill stalkers in 25 hits
Marines with 0 attack upgrade kill stalkers in 30 hits
A 20% increase
Colossi kill 45 HP marines with no armor in 1 hit, 23x2 = 46
Colossi kill 45 marines with +1 armor in 2 hits, 22x2 = 44
A 100% increase (with 55HP marines they would take 2 hits to die anyway, however +1 armor allows you to stim the 55 HP marines and stil die in the same amount of hits)
Marauders:
+ Show Spoiler +
Zealots kill 125 HP +0 marauders in 9 hits, 14x9 = 126
Zealots kill 125 HP +1 marauders in 11 hits, 12x11 = 132
A 22.2% increase
Zealots kill 105 HP +0 stimmed marauders in 8 hits, 14x8 = 112
Zealots kill 105 HP +1 stimmed marauders in 9 hits, 12x9 = 108
A 12.5% increase
Marauders with +1 attack kill zealots in 15 hits
Marauders with +0 attack kill zealots in 17 hits
A 13.3% increase, slightly better than stimmed armor, much worse than non stimmed armor
Stalkers kill 125 HP +0 marauders in 9 hits, 14x9 = 126
Stalkers kill 125 HP +1 marauders in 10 hits, 13x10 = 130
And 11.1% increase
Stalkers kill 105 HP +0 stimmed marauders in 8 hits, 14x8 = 112
Stalkers kill 105 HP +1 stimmed marauders in 9 hits, 13x9 = 117
A 12.5% increase
Marauders with +1 attack kill stalkers in 8 hits
Marauders with +0 attack kill stalkers in 9 hits
A 12.5% increase, equal with stimmed marauders armor
Colossi kill Marauders with 125HP in 3 hits until the Marauders get +2 armor, upping it to 4 hits. Colossi always kill marauders that stim in 3 hits. Attack is better for marauders vs colossi.
Zealots kill 125 HP +1 marauders in 11 hits, 12x11 = 132
A 22.2% increase
Zealots kill 105 HP +0 stimmed marauders in 8 hits, 14x8 = 112
Zealots kill 105 HP +1 stimmed marauders in 9 hits, 12x9 = 108
A 12.5% increase
Marauders with +1 attack kill zealots in 15 hits
Marauders with +0 attack kill zealots in 17 hits
A 13.3% increase, slightly better than stimmed armor, much worse than non stimmed armor
Stalkers kill 125 HP +0 marauders in 9 hits, 14x9 = 126
Stalkers kill 125 HP +1 marauders in 10 hits, 13x10 = 130
And 11.1% increase
Stalkers kill 105 HP +0 stimmed marauders in 8 hits, 14x8 = 112
Stalkers kill 105 HP +1 stimmed marauders in 9 hits, 13x9 = 117
A 12.5% increase
Marauders with +1 attack kill stalkers in 8 hits
Marauders with +0 attack kill stalkers in 9 hits
A 12.5% increase, equal with stimmed marauders armor
Colossi kill Marauders with 125HP in 3 hits until the Marauders get +2 armor, upping it to 4 hits. Colossi always kill marauders that stim in 3 hits. Attack is better for marauders vs colossi.
The numbers show that +1 armor grants a severe increase for both marines and marauders against zealots, Protoss's number 1 spam unit.
+1 armor is slightly worse against stalkers for both marines and marauders, but stalkers are weak anyway.
Against colossi it is amazing to get +1 armor for your marines, however +1 armor has no effect for marauders against colossi, you require +2.
Any thoughts?