The jury is still out on whether Tannehill and Cam can reach elite status, but both are largely considered solid enough QBs. Of course Cam has a huge edge in rushing which probably tip the scales in his favor, but I don't get people trying to use him as a comparison for Cam in the sense that he is heads and shoulders above him from a statistical point. He is not.
The main difference from what I can see is that the Dolphins fan base as a whole is more accepting and appreciative of Tannehill than Panthers fans are with Cam.
I will say it again, there was virtually zero threads or even posts on the Dolphins message board even mentioning Tannehill the week he laid a massive egg against the Bills preventing the Dolphins from getting to the playoffs. The exact same week the Huddle's front page was littered with threads (forget posts) criticizing Newton for not throwing the perfect pass to defeat the Saints and clinch the playoffs.