Practical differences between putting circuit complexity on the ground side vs the hot side
The problem with switched negative (or neutral in the case of AC) circuits is that the load is "live" when switched off. In normal use this shouldn't problems but during maintenance, for example, it can cause some confusion and danger. There are plenty of precedents for your approach in auto circuits where circuits are switched to ground: e.g., oil-warning lamp, interior lighting door switches, etc. 

The negative switching arrangement is popular in electronic control in the form of NPN open-collector transistor outputs for driving relays and motors. Very often the ability to switch higher voltages than the controlling circuit is the primary factor in choosing this approach.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Negative side switching (always "live") and positive side switching (always grounded).

Taking a simple example of changing a light bulb, the negative switching circuit leaves the lampholder live whereas the positive switching circuit leaves it dead. At 12 V it doesn't matter too much unless there's a risk of shorting the live terminal to earth.

As good practice, I would be inclined to wire switches in the positive line.