The optimum URL structure for SEO

What is the optimum URL structure is a common re-accruing question from people building sites. They look at search results and they see a common pattern of URL structures ... Is it because these structure are better for SEO or is there another reason?

Most sites have a stucture of:

Where menu pages are one directory down from the home page and the links from the menu page are one directory down from the menu page.

This common structure has more to do with the process of building and maintaining a site. Doing something like:

Still places menu1-option1 at two clicks from the home page. The number of clicks makes a difference to how many people will see the page from the main page, and excluding the effects links landing at pages other than the home page ... how important search engines see the page.

FYI a page can have more links than the page making it more important than the home page.

For SEO the question is how many clicks is the page away from the page that has interest or links from other web sites. Is it one click away from a page that has gone virual on social media?