Or either, the ideal configuration for a 2-Stroke walks to the return of the so called “Square", which means Piston Diameter = Stroke, for the following reasons:

Necessity of Compression (the effective compression only occurs from the moment where the piston closes the exhaust port in its ascending course), for a bigger generation of energy;
Better dynamic of the gases, and linearity of its passage in the engine;
Necessity of leverage – not very reduced stroke and not very raised Connecting-Rod Attack Angle of the crankshaft.
Possibility to take off advantage of relatively lightweight pistons, ideal for high rotations with an explosion for each crankshaft turn, two power factors.

Remember that power is not more than torque x rotation, being its exponent maximum the 2-Stroke engine, with its explosion for each crankshaft turn, very rotating, with a high level of tuning in terms of power attainment, or either, very peaky, with areas and timings raised and close-ratio gearboxes.

Actually, 2-Stroke engine continues to be the best specific power engine

But in the competition engines, that impulse light chassis, and that for this reason they do not need so many torque in such a way, being able to possess greater power, the constructors opt to reduce greatly the crankshaft stroke, to take off great regimes of rotation (F1 type, with great linear movement speed of the pistons), that great piston diameter do not penalize very in consuming terms, for the fact of terms only one explosion in each 2 turns of the crankshaft (one of rest, that gives rest to the piston.
On the other hand, we can ourselves be given to the luxury to benefit with these engine quotes, the power, for the fact that the 4-Stroke engine is, by nature, an engine with torque.

Therefore, for velocity circuits, 4-Stroke use great piston diameter, short crankshaft stroke, many valves on the head with reinforced springs, the best materials, long lenght connecting-rods relatively to the crankshaft stroke (to allow that the piston has little attritions in the cylinder and facilitates the high rotations, face to the great diameter of the piston), and high compression ratio; we have also high volumes of gases, admission, exhaust, to allow the engine to breath correctly in high rotations and to allow the obtaining of power.
One another aspect, is the valve timings functioning: the distribution is conceived to open the exhaust valves more early, and to allow more time of opening and exit of gases, it makes possible greater regimes of rotation and breath for high power.

If we intend to obtain the maximum theoretical power, we must also appeal to an ignition with an order of possible explosion the most alternated possible, of form to harness high regimes, this way the engine shows it’s power and torque in a more brusque and aggressive form (in the competition this situation does not happen many times, for the fact that in circuits with many curves, where power, acceleration control and binary are fundamental factors to win).
In these cases, the manufactors create big-bang firing engine, in order to obtain a better tractability and control of the bike itself, maintaing the radical engine quotes with high piston diameter and very reduced crankshaft stroke to allow high rotation regimes with aceptable piston linear movement speed.
Or in the other hand, an engine more conventional with bigger crankshaft stroke, lower piston diameter, using radical camshaft timings and a Screamer firing order, with the most alternated explosions possible.....

The tests and know-how of each manufacturer enter there in game, but in the essential, the competition is very difficult to gain themselves with a radical machine/engine, being necessary to get a commitment between the two worlds...