I finally got the G4 instant so I can put my comparison video since both are wireless.
Both Cameras build quality is same as polycarbonate only G4 instant got outdoor weatherproof rating “IPX5” (IPX5-rated devices can handle more significant water exposure, such as heavy rain or water jets). Whereas G3 instant doesn’t.
Also the sensor is larger on G4 as compared to G3 Instant 5MP CMOS vs 2MP CMOS and it got 2K 4MP vs FHD 2MP so video and image quality is improved on G4 Instant.
The only thing you get better in G3 Instant is viewing angle 111.3 vs 102.4. Both Cameras support TypeC powered included in box 5V 2A and power consumption is also similar as G4 consume 6W whereas G3 consume 5W.
G4 Instant addition it support AI event detections and G3 instant doesn’t have any detections.
Both cameras are supported 2 way integrated audio and you should check the above video to check the audio quality as well as image quality.
Both are nearly on same price just 20$ difference as G4 Instant is 99$ vs 79$ G3 Instant on Ubiquiti US store and if you compare it with Ubiquiti India Store you can get G4 Instant at 10511 INR+ tax and G3 Instant price at 8349 INR+tax.