I'm not an expert in Heroes, but I've played quite a bit, including the fifth installment. I'll try to describe my preferences. Human Castle: 1) I always took Militia, the basic unit. The ability to critically hit and push back an enemy stack is more useful than hitting twice. Even three times won't help; there's no damage. 2) Definitely the new ones with direct attacks at any range. The ability of the old ones is too situational. 3) I also prefer the old ones. Protecting allies from ranged attacks and, again, the critical hit is more appealing to me. But the new ones are also viable; I took them in some cases. 4) A difficult choice. As a combat unit, the new one is definitely better, but the initiative... In general, it depends on the situation. In a hero's army, the old ones are still preferable. In siege battles, when playing defensively, in castles – only the new ones. 5) I didn't see much difference between them, but I preferred the new ones. They have stronger attacks and cast a punishing strike. I took them. 6) The new ones. The ability to damage two stacks at once is worth it, and I think, if I'm not mistaken, the red ones had stronger attacks. 7) Archangels. They provide healing and more consistent damage. Undead: 1) It's a tough choice. On the one hand, they're a very strong unit (for a level 1 unit), and on the other, they're archers. If you've upgraded Battle Frenzy or have that ability that gives +1 damage (or both), I take the archers. If not, I take the new ones. Although I always try to take the new ones, just for a small stack to protect the army from ranged attacks. 2) Only the old ones. They have more damage and the ability to inflict weakness. The new ones are just cannon fodder. 3) I didn't see much difference; I took the colorless, old ones. They're practically the same. 4) The new ones. They're basically overpowered. They constantly cast Stun, almost always. Considering their increased speed and HP, the choice is almost obvious. 5) In the early stages, I took the new ones, for the resurrection ability, and so on. In the later stages, I took the ones with area-of-effect attacks. 6) The old ones. They have slightly more damage, and their ability is much more practical. I still remember a battle where I won solely because of that ability. 7) I took the old ones. It's just more familiar, they're slightly stronger, and they curse. Although the new ones with their sorrow are also quite good. Dwarves: 1) The old upgrade. They have a very good ability to reduce damage based on distance. But the new ones can also be useful, as they protect against ranged attacks. 2) Again, the old ones. The new ones are only better with higher damage, but if you upgrade Battle Frenzy or that ability, the difference isn't so noticeable. And the ability to cripple and deal good damage up close is very cool for a ranged unit. 3) I took the ones that attack with their hand. After moving 5 squares, there's a 100% chance of hitting with their hand, especially with a more favorable stack size ratio. Importantly, it affects everyone, unlike the roar. 4) The white ones that critically hit. And in general, they're stronger. 5) Both are good in principle, but I took the ones with stronger attacks against a single target and a fire ball. Although launching a wall of fire to stun ranged units is also cool. 6) As a rule, I chose the Erls, the ones with fire. Although the alt is definitely good. And with a mass attack rune in a crowd... 7) The old ones are more interesting. They have more defense and a fire shield. They're just an impenetrable wall. It's a shame they only attack once per battle. Inferno: 1) The standard option. They hit harder and steal mana more effectively. 2) Definitely the alt. Thanks to the jump, they're actually useful. 3) It depends on the situation. But usually the alt; if you manage to get them into the thick of things, they'll deal damage to the entire army. 4) Probably also the alt. Subjugation is an interesting ability. 5) The alt. The aura with damage is very effective. 6) In the beginning, the standard ones, later the alt. I think it's obvious why. 7) Probably the old ones. Although the new one is tougher, -1 to initiative and speed... no. Elves: 1) In the beginning, the old ones because of their swarm, later the new ones. They're stronger, and the mutual healing with Ents is a good thing. 2) Only the new ones. They're a very strong unit; the old ones die like flies under a fumigator. 3) Only the new ones. The choice is so obvious that it's almost embarrassing. Even with a bow, the new ones will still win when attacking medium units. There's no question about high-level opponents. The old ones will only win if they're attacking a lot of level 1 units and have a bow. But that's a very situational thing. 4) In the beginning, the old ones because of magic, later the new ones. 5) I didn't see much difference between the horses, but I prefer the old ones; they suppress magic well. 6) Only the old ones. The purpose of the tree is to protect the archers. The longer it lives, the better. 7) Usually the old ones. The new ones are unpredictable because of their random breath; they can even hurt their own units. Dark Elves: 1) In the beginning, the new ones, it's very convenient to harass neutrals. Later, I take the old ones, to shoot and poison. Especially if they have a bow. 2) The old ones. Initiative is more important than HP for this unit. 3) The new ones. They're tougher in defense and better suited for me. 4) Only the old ones. This helicopter is no comparison to the charge. 5) Probably the new ones. They're faster and spray acid. They're somehow more dangerous. 6) The old ones. At least one archer should be there. 7) It depends on the situation. The red ones are also interesting, and quite a lot. Cast vampirism, and the dragon is practically unkillable. Mages: 1) Probably the new ones. They seem to be stronger, if I'm not mistaken. And sometimes it's useful to blow away a dangerous ballista or catapult during a siege. 2) The old ones. The new ones have strange abilities. 3) Also the old ones. Endless retaliation is great. 4) I took the ones with the fireball. Because of the fireball. 5) The new ones. They're tougher and seem to fly further and can reach the enemy immediately, unlike the old ones. And they even look nicer. 6) As a rule, I took the Rakshasa, the sweeping attack is really cool. 7) They're the same, but the blue one's cloud isn't very good; the old ones are more effective with lightning. Orcs: 1) The ones with the trap are somehow more interesting. They're more useful; reducing the path by 1 square is enough to prevent the most dangerous stacks with a speed of 8 from reaching you. 2) They're practically the same, but I took the ones that don't have a penalty in melee combat. 3) I took the Warg... well, you know. When they get pumped up with rage, they become practically unkillable. And the ability to deflect an attack is also quite interesting. But only the old ones for attack builds. 4) I took the ones without lightning. They cast some kind of nasty spell with each attack, which is great. 5) The leaders are more interesting. They're more durable, they boost initiative, and they have a good ability. 6) The Paokai. For the mass attack. 7) The ones with the eye. The guys with the club can destroy their own army, and I don't want to have to replay battles 10 times because of that. And the luck reduction is also great.