T1 Tanks are the backbone for early attacks in Supreme Commander. Being direct fire units and heavily armored, they are an essential part of T1 armies. Each consumes mass at the same rate constructed by equivalent builders, though their construction times and energy costs vary.
It is to be noted that other than the Aeon Aurora (a Light Tank), the other three, if placed one-on-one in range of one another, will consistently achieve Mutual Annihilation unless in close ranges, in which case Strikers defeat Mantises and Thaams consistently with very little HP remaining. At "long" range, the shots necessary to kill the Striker would have been fired before the Mantis or Thaam could take the last shot from the Striker, a stark revelation of how close the matches are).
The Cybran Mantis is not a tank, but a bot, although it is considered the Cybran version of a T1 tank. Being a bot, it is more maneuverable and can move faster than other T1 tanks, therefore it can run away from armies if it has to. The Mantis also possesses the highest rate of fire, though a lower damage per shot. With its laser's high muzzle velocity, it suffers the least from overkill. Finally, the Mantis possesses an engineering suite. It can assist engineers to build things faster, and it can also repair units, however, it has 1/5 the build rate of an T1 engineer.
The Aeon Aurora is the cheapest of the tanks (by about 3.5% of its equivalents), and is probably the most unique. It has the highest DPS and initial shot damage, and also possesses a much greater range, meaning that it can safely take out other tanks if radar is present. It also can hover, so the Aeon have a definite advantage on water maps. However, the Aurora is also the slowest tank, and, being a light tank, has around half the HP of the other T1 tanks. This means that in a one-on-one battle, assuming that the Aurora is in range of a Cybran, UEF, or Seraphim enemy tank, the Aurora will probably lose. In addition, an enemy commander will find it easier and safer to take on a group of enemy Aeon tanks, as it takes only 2 shots (as opposed to 3 for other factions) to destroy each tank. This means that once they get into range, it is often best to start pulling Auroras back from the battle, as it will keep their range benefit for longer. Note that the Aurora has a longer range than it has line of sight, meaning that it should almost always be accompanied by a Scout (which, conveniently, also hovers).