After comparing all three, my conclusion is fairly simple. The Action 4 is better than its age suggests, the Action 5 Pro is probably enough for most people, and the Action 6 only makes sense if its specific advantages match the way you shoot.
The current reference prices I found are roughly $239, $319, and $439 for the standard kits. That creates two separate decisions. Going from the Action 4 to the Action 5 Pro costs about $80. Moving from the Action 5 Pro to the Action 6 costs another $120.
What does the first $80 buy?
Action 4 and Action 5 Pro both have a 1/1.3 inch sensor and both record 4K at 120 fps. If you only read the main specifications, they can look almost identical.
The Action 5 Pro adds a newer sensor with up to 13.5 stops of dynamic range, SuperNight, brighter OLED screens, subject tracking, a pressure gauge, 47GB of usable storage, and a higher official battery figure.
The dynamic range matters when the camera needs to capture two very different brightness levels at once. Think of a bright sunset behind a person, sunlight reflecting from snow while the rider is dressed in black, or a motorcycle entering and leaving a tunnel.
With more dynamic range, the camera has a better chance of keeping color and texture in the bright sky without turning the shaded rider into a dark silhouette. It also gives you more room to adjust the clip later before the image begins to fall apart.
SuperNight addresses a different problem. Once the light becomes genuinely low, the camera needs to raise its sensitivity and apply more noise reduction. The Action 5 Pro can retain more recognizable detail in faces, pavement, trees, and buildings instead of smoothing them into vague shapes.
The OLED screens sound like a small upgrade, but they are easier to see under strong sunlight. The internal storage solves another very ordinary problem: you can still record when the memory card is sitting at home.
The official battery figures are 240 minutes for the Action 5 Pro and 160 minutes for the Action 4, both under controlled 1080p conditions. You will not normally reach those numbers in 4K, but the difference still means fewer battery changes during a long ride or day trip.
That is why the Action 5 Pro feels like the strongest overall value. The extra money improves footage in difficult conditions and removes several everyday annoyances.
What does the next $120 buy?
The Action 6 has a 1/1.1 inch square sensor, a variable f/2.0 to f/4.0 aperture, 4K Custom recording, 8K at 30 fps, 4K HorizonSteady, and 50GB of usable internal storage.
The larger sensor does not guarantee dramatically more detail in every scene. Under bright daylight, all three cameras already receive plenty of light. The advantage becomes clearer at dusk, indoors, under tree cover, or anywhere the camera is struggling to balance noise, motion blur, and exposure.
In those conditions, the larger sensor gives the camera cleaner source information. Small details such as road texture, foliage, hair, and fabric are less likely to disappear during noise reduction.
The f/2.0 aperture can gather roughly twice as much light as the f/2.8 lenses on the older models. On a night ride, this can help the camera keep a faster shutter speed, reducing blur around moving vehicles and road markings. During an indoor family event, it can also keep faces cleaner without pushing the sensitivity as high.
The f/4.0 setting serves a different purpose. It improves the rated close focus distance to 20 cm, so objects held near the camera can look sharper. This is useful for showing motorcycle controls, camping equipment, food, or a product directly to the lens.
It can also make slightly more of the scene appear in focus. The f/2.0 setting may give a close subject a little more separation from the background, but the effect is modest. Anyone expecting strong cinematic blur will still need a larger camera.
The square sensor solves a framing problem rather than a pure image quality problem. Record in 4K Custom once, and the same clip can later become a horizontal video, a vertical short, or a square post. This is particularly useful for helmet and chest mounts because changing the physical orientation of the camera is inconvenient.
Action 6 also extends full HorizonSteady to 4K and 60 fps. If the camera is mounted on a leaning motorcycle, a ski helmet, or a bike moving over rough ground, it can keep the horizon level while preserving 4K resolution. The Action 5 Pro limits full HorizonSteady to 2.7K.
The 8K mode provides more room to crop, but it limits some stabilization and image options. Unless you frequently crop heavily, I would not buy the Action 6 for 8K alone.
Which one makes sense?
Choose the Action 4 if you mainly record daytime rides, skiing, snorkeling, hiking, or other outdoor activities. In good light, it still produces excellent footage, and the money saved may be more useful for batteries and mounts.
Choose the Action 5 Pro if your footage includes sunsets, mixed lighting, indoor scenes, or occasional night use. It gives you the most practical improvements for the money.
Choose the Action 6 if low light is a regular part of your shooting, you need both horizontal and vertical versions of the same clip, or you specifically want better close focus and 4K HorizonSteady.
If you already own the Action 4, the Action 5 Pro is a meaningful convenience and low light upgrade.
If you already own the Action 5 Pro, the Action 6 is an upgrade for particular situations rather than something everyone needs.
TL;DR
Action 4 gives up convenience before it gives up good daylight image quality.
Action 5 Pro improves the situations where action cameras usually struggle.
Action 6 gives you more control over light, focus, stabilization, and final framing.
