Points discused here.
1. Low Viz - ( 0- 5 m)
Advantages
You look more closely and find interesting critters, fishes are less scared of you and are nearer, you swim slowly and observe more instead of a big game fish you saw on the blue horizon, you take more care of your depth and air supply
Disadvantages
You can loose your buddy easily and buddy lines are a real hazard on a reef or wreck.
2. Good Viz ( > 5 m)
Advantages
Loosing your buddy is less likely.
Photography is more easier
Disadvantages
You normally forget you depth as you can stil see the boat, you need to take care of your air as you go deeper.
You start focusing on too many things as you can see better and miss out lots of stuff
(depends of person to person and their interest)
3. Buoyancy
Viz has hardly anything to do with it. Buoyancy comes naturally as you progress like driving. You only have to work harder to get it at the begining.
Maintaining buoyancy is easier in deeper dives than shallow dives but again its not a problem if you dive regularly ( atleast on every weekend). I prefer diving with least weight and almost no air in the BC . On a rebreather again its a different matter instead of your natural lungs the counter lungs does it, so you have to make consious effort to adjust, more difficult.
4. Shallow Vs Deep
You see more marine life at shallow < 18 m than at depth
In my experience ( which is 120 dives only) I tend to see more fish life at 3 m compared to 14 m. At shallow, surge is a problem but if you stay low its not dificult unless big waves are breaking over the rocks.
