Currently, I don't know of any way to tell if one planet is marginally bigger or marginally smaller than another in the game. (so that I know I can annihilate one moon with another, for example) First of all, is there a way to tell that I am missing? The number of engines required doesn't mean anything, for one. If there isn't a way to tell (besides building hallies obviously) then there should be, because as it stands, whoever creates the system has a huge advantage in the late game.
I'd like to second this. And add something else: There's no quick way to check the game lobby for planet sizes. Sure, the system is shown visually, but I have no idea if it's a moon-sized object we're fighting on in a 4 player FFA or if it's something huge.
We should be able to fire big planets into small ones and have the small one crater the large one. And if they're around equal size it should make a mess ^^