It depends on your point of view. There are two options you may be confusing, Bing Data and Photogrammetry. Bing Data is the one you REALLY want to have turned on. With it off, you can’t have Photogrammetry, and the scenery returns to FSX like in how it works and looks. WIth Bing Data on, that allows the Black Shark AI to populate buildings where they belong and use textures from Bing Earth.
Photogrammetry is essentially a 3D scan of an area (except it has a tough time recognizing when there’s an “underneath”. This can make scenery even more realistic as it also captures textures and applies them to buildings and the like. It’s limited, however in that only a few areas of the world have been 3D scanned that Microsoft has access to. Google Earth has more Photogrammetry than Bing does, but, Bing is working at increasing it.
Photogrammetry is much more data dense than Bing Data, so, especially for those people who have slower internet access (not just to your provider, but you could also be affected by the servers your provider accesses), turning off Photogrammetry might help in peformance. It is independently controlled from Bing Data, so you can turn it off and still get the Black Shark AI buildings and layout and Bing Data textures.