Should you sign into browsers or not?

In for ex Microsoft Egde, Chrome etc you can sign into the browsers for syncing bookmarks, etc.

And on apple devices you can opt to sync Safari to icloud which essentially is like logging into the other browsers like I describe above.

What I am wondering is if it is any negative aspects with logging into a browser, or if it's just positives?

For ex, can Microsoft, Google and Apple see and connect my search history if I stay logged …

browsers privacy sign