JohnHwangDD wrote: - they just don't sound as good (i.e. win as much).
And therein lies the problem. No army list should win more than any other. That is why balance is so critical. And "sound as good" is a reflection of taste, much as the background and how the army works should be a reflection of what the owner's playing style is and what image the owner wanted for his/her army.
If a player wanted a shooty, gritty army, s/he might choose guard. If a player wanted a technological, anime feel with mobility, s/he might choose Tau. Or if a player wanted an alien hivemind, s/he might choose Tyranid. But these choices
should have no impact on how likely the army will win/lose. It should be based on background and feel. Winning and losing should be solely determined by skill.