The Wagner 905 and 915 is the same thing on functionality. They can help remove wallpaper, steam and sanitize your floors, clean barbeque grills, greasy stove tops, etc..
The difference between the Wagner 905 and 915 are as follows.
The 915 is a newer model, it is better looking, but this is personal preference.
The 915 carry handle is redesigned, it is not attached to the unit housing with a screw anymore.
The 915 is also better constructed, it has thicker plastic shell and better wheel design for easier moving.
According to customer reviews, the 915 has shorter cord and shorter hose.
The 915 has one red indicator light and one green light, when power on, both lights are on, this indicates that it is warming up. When the red light turn off and only the green light is on, this tells you steam is ready.
While the 905 has only the red light, when it is producing steam, the red light is on, when the steam is ready, the red light turn off.
The 915 comes with 2 utility brushes while the 905 comes with 4.
Both of them come with 2 extension tubes for good reach, a wallpaper steam plate for removing wallpaper, floor cleaning head and pad for cleaning and sanitizing surfaces, squeegee for cleaning window, tile surfaces, etc.,utility brushes for cleaning greasy spots.