The best choice for recreational diving due to the essentially unlimited lateral range of movement.
With a floating gas system, the divers easily tow the floating unit along with them, so they can move about without restriction in range.
In contrast, with the deck units (e.g., electric units and deck-mount gas powered units), the lateral range of movement is restricted by the length of the hoses. (Although it is possible to use hose extensions to lengthen any hose.)
Floating gas powered units can also be used as deck units when desired, by simply not inflating the float. The engine/compressor case has white rubber feet to protect the deck.
Deck-Mount Gas Powered Units
Primarily used for commercial applications in which the unit will be operated from a boat or other platform.
Used for a variety of commercial applications (e.g., boat and other marine salvage, marine construction/repair, aquaculture, marine survey, scientific diving, in-water boat repair/maintenance, etc.)
Sometimes used for recreational diving when placed in a dinghy or similar platform.
Often used by boaters who want a compact, lightweight system that enables them to dive under the boat when necessary (e.g., unfoul a prop, clean the hull, free an anchor, etc.).
Can still do a little recreational diving around the boat. Also used for a range of commercial applications (e.g., boat hull cleaning, aquaculture, dock construction/repair, large aquarium work, pool maintenance/repair, etc.).
Electric units are quieter than gas units when noise level is a factor.