Google Sites

Pros: Extremely easy to use - drag & drop editor.
Clean, simple interface.
Pre-made designs and templates.
Completely free.

Cons: Too simple / bare bones for any practical use. It cannot be used to create a basic fully functioning website.

Overall: Google Sites is really not a website builder, it is more of a webpage builder which is good for presentation or ' design your first webpage' tutorials. Although it is really simple to use but with very less practical use.

Pros: Very easy to use.
Decent UI customization options.
Responsive web pages - works well on mobile.
Free to use.

Cons: Not really a website builder, it is just a webpage creator to show off your project or resume.

Overall: Google Sites is a pretty basic webpage creator and not recommended if you want to create a website. It lacks any form of advanced customization, integration or features like SEO, analytics.

Pros: It's very easy and the best option who don't know much about coding or website building process. It helps you build the most optimized. Easy drag and drop to design.

Cons: Overall it's an outstanding website builder platform.

Overall: It's an easy and reliable platform to build websites. Overall I used Google Sites in the past, it provides me the easiest way to build with HTML embed options and most important all its services are free.

Pros: (+) Free of cost, easy to use, and very good interface, One can go live almost instantly without waiting for approvals.
(+) Works well for small projects and individual projects.
(+) Easy to use drag and dropping option.
(+) One can add youtube videos easily, embedding are good.
(+) Integration with google applications, embedding from drive, slides, sheets

Cons: (-) Format changes are very limited (Styles and templates), you cannot push further with sites.
(-) Because of extreme simplicity security can be a concern.
(-) Not very mobile application friendly.
(-) Publishing a custom domain is not possible.

Overall: I have hardly used google sites once or twice to test it out. The application is quite user friendly and you can host your site within no time. There are a very limited number of templates and can look plain and simple. You can easily integrate and collaborate with google drive, slides, youtube, google sheets, and many other applications. For a project of very small size google sites can be a good option but for bigger projects where you need a lot of other features and customization is a key sites will not be of much help.