As said - its all personal choice. I prefer a wrist mount.
I may only check my air 3-4 times during a dive, so a small air pressure gauge spends most of its time clipped to a D ring: keeping things streamlined and tangle free.
I refer to my computer every few minutes during a dive. The easiest, most accessible spot to mount it is on my forearm.
The downside of the wrist mount is that your computer can get pretty worn if you like putting you hand down holes, such as when looking for crayfish (lobster). I mount mine further up my forearm because of this. On the other hand I have watched many computer consoles being dragged over the reef for a similar effect
Another upside of a wrist mount is that you are far less likely to have a tank dropped on it during set up or packing.
Cheers,
Rohan.