At the constitutional convention of 1787,
supporters of the virginia plan and supporters of
the new jersey plan differed over the method for
(1) determining congressional representation
(2) selecting the president’s cabinet
(3) adopting the amendment process
(4) giving powers to the executive branch

The answer is (1) determining congressional representation.

Virginia Plan was supported by large states because it stated that congressional representation should be proportional to the population of state, while New Jersey Plan was supported by small states because it proposed equal representation in Congress no matter how big the state was. 

Hope this helps~