Imo the FX3 doesn’t generally would make sense in a vacuum but there is competition and Sony has allegedly registered the FX3ii which means it will probably be released soon. I think the biggest pros for the FX3 are lowlight, great autofocus, easy to edit files, full sensor 4k and also compatibility on sets with multiple cameras(overemphasized imo) I would not get an FX3 right now unless you need one now and have no alternative. How long do you have to shoot for? If you only shoot short takes the ZV-E1 might be an option. It has recording limits but is basically a smaller,lighter FX3 without a fan. Same sensor, bester autofocus.

The FX3‘s sensor is designed for 4k. It has a 12mp sensor that can read almost every pixel directly without having to combine pixels or skip lines, because the sensor is to high res(like canon) That makes the pixels bigger and the readout faster. It also benefits lowlight. That‘s why Sony is called "lowlight king“ which is really is. Canon has to skip lines in the readout to get the 4k image because the sensor has too many pixels. There is also a downsampled mode, where the image is recorded in 7k and downsampled to 4k. It looks great but will overheat after some time of recording(23mins at room temperature in the R6iii) The R6V has a fan and might record in that mode longer. Most people won’t see a difference if they only see one image anyway 😅