Terrakion by far, thats why its in the OU tier and the others are not. They have the same total Stat points at 580 but how they get there are different. Terrakion has more Attack stat than the other two. Virizion has more Special Defense Stat then the other two. And finally Cobalion has the best Defense Stat of the three.They all sit at the same HP and Speed Stat. But what puts Terrakion over the top is its ability to come in and hit everything hard and fast. It can easily take care of the other two rather its with Close Combat or X-Scissor. Now dont get me wrong all three of them are good, heck I even like Cobalion the best, but its no match for Terrakion. Now my personal favorite is Cobalion but based off of everything that makes up the metagame, all fingers points to Terrakion.