OpenRA

Let's assume, for the sake of argument, that one side could have an advantage on certain types of map. So let's say the Soviet side has an advantage on island maps like bombardment islands. 3 Soviets against 3 Allies would have a noticeably improved chance of winning. (Assuming players of equal-ish skill.) Actually you would probably be better off with 2 Soviets and 1 Allies on the same team to get a chronosphere, but anyway.

Or let's assume that Allies' artillery gives you an advantage on maps with chokepoints.

Is this anything to worry about? Do you try to balance for all possible circumstances?

Or do you say it's not a problem if they are more or less balanced broadly speaking across a variety of map types?

This is always going to be the case unless factions are more or less symmetrical.

Its more worthwhile to try and create a map pool which results in balanced games rather than try and generally balance factions. Its also much easier to buff/nerf units for a certain map pool than to try and make them balanced for all possible circumstances.

Murto the Ray wrote: ↑This is always going to be the case unless factions are more or less symmetrical.

Its more worthwhile to try and create a map pool which results in balanced games rather than try and generally balance factions. Its also much easier to buff/nerf units for a certain map pool than to try and make them balanced for all possible circumstances.

Correct. Map pool is the keyword here.
Unless factions are similar up to a very high degree, the map layout is going to stay the deciding factor. Map size, layout (choke/open-ness) in general are going to dictate the faction's usefulness.