Another thing distinguishing them is that Thomas has been used as a gunner on special teams while Starling has been used as a return man. Thomas has had experience at Texas returning kickoffs, but I don't know if he will get a chance to try that as a Texan.
Starling has also been used regularly as a gunner. He's also been returning kickoffs in practice and had one ko return that I can remember at Pitt. We will probably see him return more ko's against Denver. I only went to the half dozen public practices but I never saw Thomas get any work on returns. Albert Johnson was usually the other guy back there with Moses, Duff, and Starling.