With Sony FX3, you can record your videos at a highest resolution of 3840 x 2160 at 120p, 60p, 50p,30p,25p,24p fps with bit rates up to 500 mbps and save in MPEG-4, XAVC S, XAVC HS, XAVC S-1, H.264 and H.265 formats. Sony FX3's 4K is the common standard resolution in consumer video world.It is also a big step up from its predecessor which has a max video resolution of only. If you are thinking of upgrading your and shoot a lot of video, this is a big factor to consider in favor of FX3.
A great advantage of Sony FX3 while shooting video at max resolution of 4K (UHD) is that there is no crop factor so you can use your lens with its actual focal length.
FX3 features a high speed mode where it captures videos at 240fps which helps to create slow motion videos. If you shoot a video at a frame rate of 240fps and play it back at 24fps, the video will be 10x slower and longer than normal.
FX3 has a built-in Stereo microphone and a Mono speaker. Sony FX3 also has a port for an external microphone and a headphone port for connecting external headphones which make Sony FX3 a very suitable camera high quality videography.
Sony FX3 also features an Digital Video Stabilization mode where videos are stabilized in-camera while you are shooting. Keep in mind that this effect may crop your videos a little bit and doesn't help stabilizing still images. This kind of video stabilization effect can be replicated by using some of the advanced video editing softwares in your PC.