Cars.com and autotrader don't count their VDP's and SRP's the same way (purposefully I'm sure), and their selling model is different. It makes them almost impossible to compare statistically. On top of that, all manufacturers and markets are going to perform differently. I always look for consistency in call to action conversion from within the VDP, as well as consistency in the ratio of SRP's to VDP's. As long as things aren't all of a sudden falling off, I'm generally not going to rock that boat. I work at a highline store and often have rare and expensive used cars for sale, so having a national presence is important to us and makes nationally known vendors a must.