DxOMark:

The iPhone 7 achieves an overall DxOMark Mobile Score of 86. That’s better than Apple’s previous best score of 84 for the iPhone 6s Plus and 82 for the iPhone 6s. Its improved Texture performance is likely related to the new lens design, while its lower noise score shows the effect of its faster lens and improved image processing chip (ISP). Artifacts are also greatly reduced, thanks no doubt to the upgraded ISP.

It still loses out to the HTC 10 and Samsung Galaxy S7 in DxOMark’s ranking, but it does have a smaller sensor behind the wide-angle lens. In real-world use the different is negligible however, especially if shooting RAW. If anything, from my own tests, the iPhone 7 has ever so slightly less shadow noise than the SGS7. JPGs are another matter entirely, with Apple’s ISP being subjectively superior in my tests — the Samsung images are much punchier and have a higher contrast, which results in detail loss, especially in the shadows, while the more natural iPhone shots allow for more post-processing, including going for that high-contrast look that so many people prefer.