We have just seen a little bit of both in the two preseason games. Right now most of their body of work has been in practices which we haven't seen. Even though I am a Longhorn fan I can see that Starling has pretty special talent, so I would have to guess that he would end up with a spot on the roster if I had to chose between Starling and Thomas. However, I haven't seen how they have done in practice. 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.
Since AJ won't be playing against the Broncos we should get a chance to see more of these two guys, as well as Armstrong. Armstrong will now be in the starting 3 WR packages, while either Starling or Thomas will be in the starting 4 WR packages.