Well, saying 'best unit' is a very general term.
It really all depends on lots of things:
1) What race are you?
-This pertains a lot to best unit, because each race has it's own units, and each of them work differently with
other units. The kley is not to pick one unit, but mix in lots of unts, not too many, about 3-5 different types, and utilize them. Casters are very good working with melee or ranged units.
2) What units are you using it with?
-Massing
does work, but it won't get you very far. A smart played knows how to counter a mass/rush, so figure out which units you want the specific unit to work with, this allows for a very powerful army.
3) Air or ground?
-Are you going to go air, ground, or mix a little of both? Certain units work better with ground then they do with air, and vice-versa.
So, as you can see, just picking
one single unit is very a difficult task.
-Frank
