This is a bit of a geographical issue. If you're using Dealer Specialties for your photos, their back-end tool is quite good for posting to Craigslist. Both Dealer Fusion and Dealer Specialties offer you an editor which is good for enhancing your listings and highly recommended as the comments go where they feed your inventory. Probably even to your website(s).
For the pre-owned I have had better luck with Cars.com (subscription vice per lead) program. Either program (autotrader or cars) needs a little more work than just paying!
Somewhat smaller sites offer basically the same services that the “bigger” auto classifieds companies offer at nowhere near the prices the guys are paying. Your listing will be just as likely to be found on our site through organic Google, Yahoo or Bing searches, as it would be on the bigger classifieds sites.
Plus, using sites other then the “bigger” sites also means your vehicle(s) will more likely be seen. In turns means it’s more likely to be sold, cause you can’t sell it if they can't find.