For real estate photography, the main practical advantage of moving from Nikon DX to FX is access to a wider rectilinear field of view for interiors.

That matters because room photos often need to make spaces feel as open and spacious as possible. A full-frame body can use very wide lenses that don’t have an equivalent on DX. For example, a 14mm full-frame lens gives a view that would require about a 9.3mm rectilinear lens on DX, which effectively doesn’t exist in Nikon’s lineup.

So the real gain is not simply “full frame is better,” but that FX lets you shoot wider without using a fisheye lens. Fisheyes can go wider, but they introduce strong distortion that usually isn’t desirable for real estate.

That said, DX can still be workable if you use an ultra-wide rectilinear crop lens. A lens like an 8-16mm APS-C zoom gives roughly a 12-24mm full-frame equivalent field of view, which may be enough for many spaces.

In short: upgrade to FX if you specifically need the widest possible rectilinear interior views. If your current results are good, a DX ultra-wide lens may be a more cost-effective step first.