At higher levels smart self-defence systems will function similarly, different is the most method of teaching.
Wing Chun is teaching using a more linear & structured method.
Systema is teaching using a more holistic & intuitive method.
Most of Wing Chun & Systema concepts are similar, however both way are using unique concepts.
Wing Chun & Systema are compatible systems and we can train Systema according Wing Tsun principles and still train Wing Tsun to apply Systema principles.
Finally both methods complement each other & allow you to learn quicker.