When it comes to systems depth in MSFS, my personal preference is for addons that provide highly accurate and detailed simulations of the various aircraft systems. This includes everything from the fuel system to the hydraulic system, electrical system, and engine management.
For example, in a typical airliner addon, I expect to have access to detailed information about the various engine parameters such as the thrust, EGT, N1, N2, and fuel flow. I also want to be able to control the engine thrust reversers and accurately simulate the startup, taxi, and shutdown procedures.
In terms of the fuel system, I want to be able to accurately manage the fuel load and balance, and also to have access to detailed information about the fuel pumps, valves, and filters. Additionally, I want to be able to simulate the various fuel system failures that can occur in real-world aircraft.
For the hydraulic system, I expect to be able to simulate the various hydraulic pumps, valves, and actuators, and to have access to detailed information about the hydraulic system pressure and flow rates.
In terms of the electrical system, I want to be able to accurately simulate the various electrical generators, batteries, and bus bars, and to have access to detailed information about the electrical system load and power distribution.
Overall, my preference for highly accurate and detailed systems simulations is driven by my desire to fully understand and control every aspect of the aircraft, and to be able to simulate real-world airline operations as accurately as possible.
So far, The Fenix A320 has pumped up my energy to the roof.