Control is obviously closely linked to share ownership, in the sense that where ownership is over a certain threshold you will be able to exercise a much greater degree of control than below that threshold. For example, the 51/49% split, but also, in the UK, where you have power of veto over major decisions requiring a special resolution with 25% or more.

However, I would be interested here to understand how two people with different shareholdings are able to exercise equivalent levels of control (again on the assumption that each share attracts one vote).

This assumes that control is being assessed on a pure basis without taking into consideration the psychology at play between different shareholders.