Hi Curtis,
Thanks for your reply. Well to be more specific the domain would be:
freecarfinder.com/cars-that-start-with-a/
The domain is new so it has not authority whatsoever. The domain is not that long but it's not really short neither. The content on the page is pretty small where the exact keyword that's in the URL is mentioned in the heading 1 and twice on a small piece of text that explains how to use the page to search for results.
Totally agree best practise is to test it out. I do see that our competition is using /starts-with/a and is ranking really well with it. Maybe the best option is to create half of the pages using the exact keyword in the URL and half with /starts-with-a/ to see which one performs better?