As Stefan Ruitenberg explained in his article, even more stringent rules saw the end of some ingenious designs as seen on the Mercedes F1 W05 or the Lotus E22. As he also mentioned, little room appears to be left for design freedom.
However, with the first pictures of Force India's supposed solution (the nose was featured on a VJM07 chassis so there could still be a small chance this is not the real nose) and Williams' solution, we saw two very distinct designs. With airflow underneath the nose still crucial, each team followed its own aerodynamic approach while incorporating the longer internal crash structure.
At first sight it would be easy to conclude that the Williams solution allows for more airflow underneath due to its boxy design, dimensioned to fit the minimum dimensions as stipulated in the Technical Regulations. But is this truly the case?
Below I have drawn both nose cones, the Force India solution on the left, Williams' design on the right. Both are drawn from the same perspective and scale to ease comparing. Considering head-on airflow, the Williams solution appears to be superior.
However, it's crucial to realise that downforce is most needed when cornering, a point where the car is in yaw. At this moment, airflow will not hit the car straight on, but with an angle. It's an indispensable factor in nose cone design on modern F1 cars.
Suppose the car is taking a sharp turn to the left, which results the airflow taking this angle on the car:
As you noticed, the thickness of the air volume is left constant to make comparison easier. It's still tough to declare a clear winner, but it appears like the Force India design, or at least the one that was on display, allows for slightly more airflow underneath the nose cone while the car is cornering.
How is this possible? Is this F1magical all of a sudden? Of course not. Force India very consciously moved the 'thumb' part of the nose forward over the neutral section in order to have less obstruction in between the front wing pylons.
Note that while this does highlight one design aspect of nose cones, it does not mean the Force India nose is better overall. Other parameters like influence on the neutral section and airflow structures are just as important as well.