If you have a look at the videos, you can easily notice that it is the OIS that makes difference here. Lumia 925 videos are smoother and steadier due to OIS but Lumia 730 video capture is also very good for its tiny sensor and without benefit of OIS. Even in low-light conditions, Lumia 730 camera gives good fight to Lumia 925 camera with help of the Lumia Camera 5 algorithms and its F/1.9 aperture.
In a nutshell, Lumia 730 camera really impresses and with Lumia Camera 5, it gives Lumia 925’s PureView camera a run for its money. If you want better low-light / daylight imaging and smoother video capture you can think about Lumia 830, that our comparison shows, beats the Lumia 925 camera hands down even without Lumia Camera 5.