Which URL name is better?

Agree. From SEO perspective this seems to be the best option.

Thanks. I see many sites with layered directories and wondered if that was an SEO trend. I also believe that "flatter" structures are better.

Wrong. Look up siloing.

Maybe after 4 deep, there is some drop off, but if you organize your site well, nothing is more than a couple of links from the surface.

Personally I tend to silo on the sites I build simply because I do them manually. Siloing is a logical organizing of pages from both a webmaster and taxonomic perspective if done right.

My urls are what they are only because of organization. For WP you can use %postname%, but I hate the look of
example.com/five-key-things-you-should-know-before-you-undertake-an-seo-campaign-to-improve-rankings/. Keep it down to a few keywords if you believe what Matt C says.

Personally for the two WP sites I have, on one I use %postid% and on the other I use the default with the variable. Both rank well and I'm outranking sites that if you look at their seo, should outrank me, not saying it's because of my url, but I think the general populace may be starting to equate really long keyworded urls with spam, so they are clicking around them.

I don't buy into the importance of keywords in the url at all. The keyword domain is worth way more. Titles are far more important than urls. A url is a pointer to content and that's it. Keep keyword stuffing them and they'll matter less and less in the algorithm, if they ever did matter.