|This is how theorists and statisticians see MinMax|
Minmax is a decision rule used in decision theory, game theory, statistics and philosophy for minimising the possible loss for a worst case scenario. At least that's the Wikipedia definition. In Warhammer the term generally means minimum cost, maximum output. This can manifest itself in many ways and I'll talk about as many of them as I can.
On a unit level, this usually means taking the minimum size unit while being able to take the maximum equipment or upgrades to maximise it's output.
Example time: Chaos Chosen are a great example. Units of 5 models, each of them with a special weapon upgrade. The minimum sized squad in order to get maximum damage output. In this example there is a sacrifice the Chaos player needs to make in that since the unit is only 5 models, their damage output is greatly reduced for each casualty they take.
However, this manifests itself very differently in different units. Termagants for example, become far more useful when they are in a unit of 30. This allows the Tyranid army to take a Tervagon as a troops choice, allowing them to still take the all mighty Flyrant. The fact that there are 30 Termagants is irrelevant because they are nearly useless, even in units of 30. They mainly become worth their points cost because they can make a Tervagon as a troops choice.
And Orks manifest this idea a third way. A unit of Orks becomes more useful the larger it is, and the more characters it has. This makes it more resilient hopefully keeping enough models alive to still be strong enough to do damage once it hits home, and to ensure it gets a useable result on the Mob Rule table. Shooting units in the Ork army work the same way. Due to their terrible BS, an Ork unit only becomes useful when the squad is large enough to score a decent number of hits. Although the term MinMax may not really be appropriate, more like MaxMax.
Another way Orks use this tactic is with Burna boys in a Gorka/Morka naught. Taking a small unit of Burna boys allows the Ork player to get a maximum number of Meks for repairs.
Finally, Eldar use this method of taking small units of troops choices in order to take a Wave Serpent transport. Although this was far more prevalent in the previous edition of the Eldar Codex, the Wave Serpent is an extremely strong vehicle and one of the main reasons that small units of Dire Avengers ever see the table top.
In an army wide scale, this sometimes take on a different approach. In a Battle Company, often times it will include 3 units of Scouts as the Auxiliary choice because they are the cheapest option. They will typically have no upgrades and will mainly be used as table control units being put in reserve to outflank, or Infiltrated to put some quick pressure on the opponent and act as a distraction. This will allow as many units of marines will be upgraded to full size as possible, allowing them to combat squad, while still being able to take as many Gravcannons and Meltaguns as possible. Gravcannons may be Expinsive, but their damage output is by far greater than almost any other weapon they have access to.
Likewise, a Chaos Daemons army will sometimes take Chaos Space Marines as allies in order to get Belakor and/or a Heldrake in the army. They will take a minimum sized squad of Cultists to ensure the minimum price is paid in order to get the maximum output from the detachment.
MSU(multiple small units) style armies use MinMax units to great effect. The theory behind an MSU unit is that you overload your opponent with targets so that he can't possibly kill them all, and because each of your units are able to do damage, your opponent will not be able to kill enough units to keep himself safe from the retaliation.
Having smaller units is also a great way to nullify some of the opponent's huge damage dealing units by forcing him to unload excess amounts of firepower on an easily killed unit.
Space Marine Battle Company, Dark Eldar Venom spam, and Astra Militarum can pull off some serious MSU MinMax armies.
As I talked about in my Dark Eldar review, they make great use of the MinMax idea taking small units of cheap warriors so they can get as many Venoms as possible. Upgrading as many of those Warrior units as they can into Trueborn increases the number of special weapons the unit can take as well.
Now that I gave you all that info, you may be thinking "That description looks like all the armies I play and play against, what does a non-min maxed unit/army look like?"
Well, to give you a little clarity and something to reference, here are a couple non-MinMaxed examples.
A themed Chaos Nurgle army where all the units of Plague Marines have 7 models. Those 2 extra models are not required to get any kind of bonus so they are non-value added models. If he had 5 units of Plague marines all with 7 models, he could drop 2 models from each unit and buy a 6th unit of 5 Plague Marines.
Another thing I see sometimes is units with less than a full compliment of available weapons. A devastator unit with only 2 heavy weapons comes to mind. Now there may be a perfectly sane reason for this. In a Battle Company list where the player must take 2 Devastator squads, only taking 2 or 3 heavy weapons is a good way to have a couple spare wounds in the unit that won't cost you fire power when you loose them AND a good way to save points. Grav-cannons are 35 points each.
So, I hope you gained a little insight into how to MinMax. However, as I pointed out just above, know that it is not always the best method for building armies or units.
Until next time, keep them dice rollin.