Hamlin Reed Relays for Audio: Sink or Source?
In general, it makes no difference to switch V+ or ground.

However common practice in automotive is to switch ground in some cases and switch power in others.


in case of accidental wire shorts, the low side switch is safer if the high side is more protected.


What does matter is how the release current is snubbed with a reverse diode across the switch to the opposite rail.

Case in point, Weller for decades used a thermostatically controlled reed switch to regulate the soldering iron to a controlled temperature. They failed to recognize this little coil and wires spews out enough EMI to cause false triggers on scope or long leads in breadboard edge sensitive logic.

So at a minimum a diode is needed. Then twisted pair (UTP) wires everywhere +/- current flows to switched load. Then sometimes shielded or STP wires and then sometime a CM ferrite sleeve choke.