Which URL structure is better, and Why?

WHAT IS BETTER (assume primary word is “peanut butter” and category keywords are “crunchy peanut butter” and “smooth peanut butter” respectively)?

Peanutbutter.com/crunchy/
Peanutbutter.com/smooth/

OR

Peanutbutter.com/crunchy-peanut-butter/
Peanutbutter.com/smooth-peanut-butter/

I think 2 option is better because your keyword phrase match in url. It helps to ranking.

Given that you’ve got ‘peanut’ and ‘butter’ in the domain name, including them in the file path as well is just overkill. The more words you use, the more chance there is of people trying to directly enter the URL getting it wrong and not getting to the page. Why make it unnecessarily complicated?

But http:// isn’t going to get you very far…

I think 2nd option will be better

Peanutbutter.com/crunchy-peanut-butter/
Peanutbutter.com/smooth-peanut-butter/

Because your keyword and category both are covered. URL will be keyword rich and there will be more chances to get keyword at first page.

guys/gals, im not asking about “overkill” or what “looks spammy” - im asking purely from a crawler perspective - which is better if you want to be 100% sure the crawler knows your site’s page is about, say, “crunchy peanut butter” - which options would most-ensure this goal??

Depends on what words you are trying to optimize for. If both Crunchy Peanut butter AND smooth peanut butter (as in your example) the 2nd option is the better of the 2.

for example, how would search engines know the first example, first link is about “crunchy peanut butter” and not just “crunchy” (which has all kinds of meanings and contexts)

I think it doesn’t matters which you use

Totally agree with this. It looks a little spammy also it’s easier for you to maintain directories with shorter names

why?