Love his tenacity and aggression. At the same time, he manages to pull out of situations not to cause penalties - seen it a few times already this season. Perhaps that is an advantage of being smaller and more agile?
Also, we got to see him in full pelt yesterday against Jesus, and he was at least as fast as him, probably even faster, so he is quite fast even over distance.
I think Varane struggled a little more with Jesus in fact, but then Jesus is tricky, and when the refs allow him to run into defenders, manhandling them without any concern, only for similar contact the other way resulting in automatic freekicks, it makes defending a little troublesome.