In terms of similarities, they are both attempts to improve "perceived page speed" that actually decrease page speed or encourgae practices that decrease page speed

For example, injecting ads and tracking into web pages via connections to third party servers. This is not a practice that increases page speed

If I am not mistaken, "web.dev" is operated by an ad services company

As a web user, not a "web developer", I use clients that do not "support" these "features". For me, YMMV, this makes information retrieval from the www much faster and more resource-efficient than if I tried to use clients that do, such as the so-called "modern" browser

There are also privacy and security implications associated with choice of client, however these are not the primary reason I choose clients other than the so-called "modern" browser