Oxygen Sensor 4 wire - all the same?
 

My car has Bosch 02 sensors. One is bad (downstream).
Will any 4 wire 02 work?

I have a Standard SG1273 (no connectors) which is supposedly interchangeable with DENSO 2344209 / BOSCH 15733

Rockauto shows for my car:
Standard SG243
DENSO 2344667
BOSCH 13550

Aside from the connector, are there any differences between those 4 wire O2 sensors?

Or will any 4 wire O2 sensor work?

The O2 sensor outputs a certain voltage according to what it reads from the exhaust. So you should buy an O2 sensor designed to work with your ECU, otherwise the ECU might misunderstand the readings.

From the documentation I have seen so far, the signal (=voltage) in response to changes in O2 content does not seem to be different (probably using the same physical principle and materials).

Any proof for you statement?

Only found wattage difference in the heaters.

There are 2 types of narrowband O2 sensors, titania and zirconia. Most cars use zirconia sensors and they're all interchangeable as long as they have the same number of wires, even then you could get away with using a 3 wire sensor in place of a 4 wire if you really had to. Not sure what the B5 uses though.