Hey man, I know it must seem disappointing. A floor model Ares is decent for a tank but in terms of HP (bot and shield) is second to the Juggernaut even when maxed out. It has the same energy as a Juggernaut well: 3 star (12), 4 star (16), 5 star (18).
it is vulnerable to javelins, mortars, side & rear attacks the same as any other mech except Juggernaut. You have to consider what role you want it to play in your hangar. The role of a tank is to take damage and let the assaulters deal it. You want to use it to hold tight spaces, ramps and corners while the other blues reload. When thinking about what to spend your hard earned credits and a-coins on, please consider the following:
1) At 4 & 5 star Ares can deal its fair share of damage and if you have picked your spot carefully you will be the spot that the light bots will learn to avoid or die.
2) The wide shield helps protect bots to either side of you from direct fire and will keep them alive to support you longer. Think guardians, panthers and zephyrs who are super squishy at close range.
3) Always remember, the support robots will cover your flanks, the assaulters will cover your advance but the TANK IS THE ONE WHO KNOCKS!
Have fun with whatever bot you pick!