Depends on:
Model
Age
Environmental exposure,
Mileage
Generally I find BMW Electrics rather good, newer stuff tends to have module failures so that is a debatable issue. Older stuff (pre 2000) is typically the most logical and simplistic type, using separate wires for each function linked to relays and sensors. It's easier to modify and change around IMO.
Newer stuff, early 2000s on, went to a CAN bus (or similar) system that uses single wires between modules to communicate, basically like a Ethernet system within your car. If you have the means to use BMW diagnostic software it's pretty awesome at solving problems and getting live telemetry from the cars sensors so you could argue it's better than the older pre OBD2 CAN systems. However the complexity does go up with that.
I personally like the older style as it's all fairly straight forward, if maintained properly, would last for decades. E30 / E34 era etc.