The correct answer is representation.
At the constitutional convention, big and small states fought constantly over representation in the legislative branch (also known as Congress). Having power in the legislative branch is important because this branch makes federal laws which all citizens are expected to follow.
Big states wanted representation in the legislative branch to be based on population. This would allow larger states, like Virginia, to have more power in terms of making laws. However, smaller states wanted equal representation in the legislative branch. That way each state had the same amount of power, regardless of size.
Ultimately, the two sides compromised with the House of Representatives being based on a states population and the Senate having two senators from each state, regardless of population.