Which creatures from the alternative upgrade options do you choose?

The main purpose of armored units is to protect their allies from ranged attacks.

Okay, but what if the enemy has Chaos magic and uses it? Or if the enemy is a Dhalebian?
In that case, if you use an armored unit to protect a group from ranged attacks, you could lose up to half of your units.

The "Remove" spell doesn't work on Berserkers. Subjugating a hero with a lower level than yours doesn't happen very often. Plus, you can only use it once (or more with magic skills). It's not very reliable.

To be honest, I didn't know that, so I apologize and admit I was wrong.

1. The alternate upgrade for Cavern Stalker is almost always better, and it doesn't cost mana. Heroes usually have a lot of mana anyway. So, the process of using the ability is more important than where the mana goes.
2. Heroes often have the "Dispel" skill, which allows them to move around without being targeted. All demon upgrades have lower initiative, so someone will always be able to remove the debuff.

1) If the demon has magic, that amount of mana might not be enough. Besides, the ability itself is then used incompletely; you should try to use all its aspects (but not at your own expense, of course).
2) What if you're playing on a map where each player only has one city, and there are few players (or even just two)? There's a chance that the hero will learn a spell in the city. But what if no spell drops in the city? Relying on altars is foolish; the drop rate is quite low, and there's nowhere else to learn spells (unless the enemy uses one, and you have the "Uncover Secret" perk, but even then, the chance isn't that high). + If a turn is made with cavalry attacking another stack (or they manage to move after the cavalry but before the demon), the Imps (or their upgraded form) won't reach them. What then?

So, without considering the abilities of both upgrades, the damage is approximately the same. The damage increase completely ignores armor. Let's say the target has 40 armor, and the Lizardmen have 20 attack. Completely ignoring armor would result in an approximate 200% damage increase. For the alternate upgrade, you need to hit 8 targets along the way. But the enemy might have even more armor.

But what if the enemy is a Dwarf? (We're talking about the "Armor" skill).
Or what if the enemies have less than 12 initiative, but more than 11? (Swift Riders have 12, which is 1 more...)