I’ll say beforehand that:
- I excluded a turbo intentionally, because turbocharging favours VVL heavily in terms of torque curve.
- The non-VVL engine isn’t strictly optimised for Automation, but represents a typical real world approach to engine designs of this type (for economy cars), with peak torque around 4000 RPM and redline around 6500 RPM.
- Both engines are biased towards maximum undersquare-ness, and have the same performance index and reliability. If reliability is relaxed, the VVL engine will likely pull ahead further in terms of stats advantage.
- Gearing for both is set at 100 km/h @ redline in 3rd gear, 51 spacing, 7 speed gearbox.
- The cars are identical but for the engine; airflow is just above requirements.
- Exhaust choked for maximum performance index.
- Only difference between engines is bore/stroke, compression ratio and valve train–same materials used.
A more desirable engine could probably be made for that car/market without using VVL (I managed it with an anaemic very small I6), but I challenge the idea that you could beat all [edit: many of 
] the stats of the VVL engine while spending less resources. In this case the VVL’s only weak points are emissions (which is negligible), and 10% higher engineering time. 0-100km/h is also slightly lower, but isn’t really significant in terms of marketability, and the non-VVL engine is faster around a race track (something not measured in terms of the in-game market).
For this specific case/market, I guess it boils down to ‘is 10% more engineering time worth 3% more desirability?’. I would stress again that with the current turbo system, the desirability disparity is actually quite a bit greater if you are trying to make a maximally competitive car.
