Here are a number of reasons why I upgraded my camera from the Sony A6000 to the A7iv. 4K Video, 759 AF points and more.
Sony A7 IV Underwater Camera Review - Bluewater Photo
Nauticam NA-A7IV Underwater Camera Housing for Sony α7IV Camera – Reef Photo & Video
Sony Alpha a7 IV Full Frame Mirrorless Camera - Body Only
Setting up Sony A7iv Enthusiast Photography Blog
Marelux MX-A7IV Housing for Sony Alpha a7 IV Mirrorless Digital
33MP full-frame Exmor R back-illuminated CMOS sensor, 8x more powerful, next-generation BIONZ XR image processing engine
Sony a7 IV Full-Frame Mirrorless Camera
Sony ILCE-7M4 A7IV Mirrorless Digital Camera Shutter Count 34 *Unused* – AGFCamera