Recs.
Updated
SpecsUpdate
Pros
Pro Booting & updating
Chrome OS boots from power off in about 7 seconds. So you don't need to leave it on and consuming power when it's not in use. You NEVER download and update any apps, although the OS does update itself. Web apps live on servers, so they're always up to date and virus free.
Cons
Con Privacy unfriendly
A system made by the company whose business model is tracking users and non-users, selling their data and serving ads. And while we're at it, switch to a custom ROM for your smartphone and if needed, get microG instead of GPlay services and Aurora Store instead of Play Store. For the other stuff there is a comprehensive list of alternatives at privacytools.io and privacyguides.org
Con Very limited in features
There aren’t really any applications you can get on ChromeOS. If you can do it via Chrome you can do it on a Chromebook, but not much else.