I am much further from being an engineer, but have always thought on general principles the Desmo valve system must actually have an intrinsic advantage in terms of efficiency/power if not power delivery in a fuel economy formula.
Yes it has some advantages as disadvantages too. Related to efficiency/power, desmo valves is better because the valvetrain is always perfect synchronous to the motion. But the advantage is not that big because modern pneumatic valves are very efficient also. The drawback is that it is a complex system and as such can take precious space and weight too much when we're talking about prototype racing bikes.
The additional upside of desmo, that often goes overlooked, is that at lower rpm the camshaft does not have to fight the tension of the valve return mechanism (a spring in conventional engines), that has to be strong enough to operate at max rpm and remains constant even at low speeds; reducing frictional losses at lower rpms does produce stronger low end torque. I'm not sure how this relates to pneumatic valves. Is the air pressure constant in those systems? If so, then desmo still would produce more low end torque than them. Or maybe pneumatic systems are even more flexible and can be calibrated to offer optimal response at all rpms?
But also pneumatic doesn't have to fight spring tension (even if indeed there is also a coil inside a pneumatic valve but is very light and used when the system is turned off)
Of course, in road bikes, desmodromic valves are much better compared to spring conventional. But we're talking MGP here, haha.
I'm not a specialist in valve systems but about your doubt, the pressure inside the cylinder of a pneumatic valve is variable and depends of a range of revs (there is a sensor detecting the piston (what pushes the valve) position and regulating the pressure). What matters the most is that it's adaptable, not as efficient as desmo but very similar, the difference is not that big even in high revs.
Yes, desmo is still better here, but... pneumatic valve system takes a lot less room to work and weights a LOT less. This translate to smaller and lighter units. And we all know a racing bike cannot win only by having some more horses.
I'm not saying Ducati must adopt pneumatic, but...
...none of those systems is the current best. Check EVA (eletromagnetic valve actuation). No need for a mechanical camshaft, which means you can precise regulate valve aperture as you want. No need of moving parts (in valvetrain obviously). No camshaft and no moving parts, no friction, no resistance, nothing... you have a component very, very small and super light, and super precise control that neither desmo nor pneumatic can deliver. Maybe it's time to upgrade the valve system (desmo is something more than 50 years old.. c'mon), the entire engine, focus in compact units. This makes a lot of difference.
