Well, they all do produce steam, yes. The differences come in the details. What is the most important aspect of this equipment to you aside from having it work? The look of the control, the size/shape of the equipment, the steam pipe run length, hard water concerns, warranty, control features, and integrated accessories (audio and light systems, remotes, etc.) are typically the deciding factors.
Since you cannot mix and match your steam equipment between different manufacturers, many times these features become the reason for the chosen equipment. If you have used the SteamSaunaBath sizing tool, you will see a "compare" box under each generator that was returned in your results...select a few generators and hit compare to see the features available. Once you see what's out there, you can decide which factor is most important to you and select your equipment accordingly. http://www.steamsaunabath.com//catalog/generator_sizing.php