One of the major deciding factors between water and air rowers is price. Water rowing machines are often found in higher price ranges with the lowest model going for $700 and the best models starting around $1,100. Air rowers are found in every price range starting at $300 and going as high as $1,000+. The affordability of air rowing machines makes them very popular.
Although the oar can be conveniently thought of as a lever with a "fixed" pivot point in the water, the blade moves sideways and sternwards through the water, so that the magnitude of the propulsion force developed is the result of a complex interaction between unsteady fluid mechanics (the water flow around the blade) and solid mechanics and dynamics (the handle force applied to the oar, the oar's inertia and bending characteristic, the acceleration of the boat and so on).
The overall rowing experience encompasses pulley, seat, and — of course — resistance. Air and water have very distinct qualities, making them impossible to compare but interesting to contrast. Air stores inertia, which feeds into intense, constant effort during a goal-oriented workout. Water’s more sluggish drag makes for demanding exercise, but one that’s less consistent.