These are two different types of detectors. The Sand Shark is an excellent ocean beach and water detector for saltwater. In the grass or woods, you'll wrap it around a tree if you are like most people because it responds really good to long iron (nails).
The Tiger Shark now has a Saltwater mode but depending on the area at the beaches this might not be enough to halt instability. I had no trouble with the Tiger Shark in FL or along most of the east coast till I hit Virginia Beach. So for Saltwater with out the fuss of constantly adjusting the GB I would use the Sand Shark which is a Pulse unit. You can't easily dial down the Sensitivity on the TS as that control is inside the box.
For dry land searching the Tiger Shark will do it well, but being a water detector it is heavier than the good land units Tesoro makes. The land detectors also have a pinpoint VCO button that makes locating the target easier.
For the most fun you really need a couple of detectors just like a golfer needs different clubs to play well.
