I was wondering how players could decide between a small army with strong heroes ( expensives), big army ( numbers of troops) and no fancy heroes or in my opinion, the must difficult one to achieve, a balanced army?

I know we have different factions and every army have its particular strategy, weakness and strenght. But how could we start building a good army, what could be a GENERIC step by step or questions that allow players to understand:

for small games is better to get more troops than power?
Medium size games are better with strong heroes?
Mix armies or just one faction?

I am trying to fing general knowledge that help me and others when we have to build warbands

I think it is often important to have one good hero in all lists to lead but alot of the time it is good to have numbers because it is harder to be broken. However some heros are pretty invinsable like beorn the bear and sauron with the ring so it is your choice really one isn't much better from the other