Champions are NEVER built. On more or less rich or long maps, you definitely need to build up to angels. In any other cases - that is, when there is not enough money for several angels - you don't play through monsters. Because 3-4 champions are weak.
For example, if I have 10 cities and 100 mines, and you only have one city, I can crush you even with leprechauns. The thing is that champions always pay off, but angels require strong funding. Although the potential of angels is higher, it's pointless to argue about that.