My favorite in this space is Applitools eyes (https://applitools.com/).

Eyes has really advances image processing capabilities, which meant two huge advantages over everything else I looked at:

1. It's not prone to rendering differences. I can set a baseline in one browser/OS combo, run it on other combinations and set it to only consider real regressions as a failure.

2. It can validate the layout of the page even with dynamic content.