Disclaimer: Last time I looked was probably 7+ years ago.What did you find was missing with the competitive sets in Max?
I probably did 50 to 75 appraisals side by side to see how many vehicles were listed in vAuto versus the other tools - since this is the data used in pricing your vehicles. I set the filters identical, set the radius the same - check them at 100 miles, 200 miles, etc. Almost every time, there were 10 to 15 vehicles in the smaller radius that didn't show up, but they did show up in vAuto. That 10 to 15 number became much larger the further you went out.
I haven't looked at other tools in a while, but at the time, I decided that having more listing data outweighed the cost savings, since that is the foundation of appraising and pricing. If some of these tools have caught up from a data perspective, then I should start looking again.