The Disadvantages of Mechs in Modern Warfare Outnumber the Advantages
Yeah, I know this is exactly the opposite of what you want, but hear me out.
* Mechs are not agile! While tanks use treads, which have enough friction to not skid or slide, mechs must balance bipedally; sliding is more likely, and will topple your mech like a person on ice. A tank will roll over in the worst case scenario, but this almost never happens; a mech will stumble or fall as long as you hit a leg.
* Mecgs are expensive. It costs more to build "movement-smart" mechs with all systems and parts in place for locomotion, coordination, and balance, than for a vehicle that simply rolls and turns. Plus, the maintenance of all the parts required for bipedal locomotion will outweigh the maintenance (and cost) for simple treads!
* Tanks are easier to repair. If your tank treads are struck and somehow unequipped, you can stop the vehicle and put on replacement treads. If your mech is struck, you need to diagnose one of a hundred possible problems, take apart the legs, and replace individual pieces, then put the legs back together.
* Mechs cannot right themselves. Once your mech trips and falls, or is struck, it will need work to be righted and rebalanced. Adding arms capable of righting a mech means more complex parts, more repairs, and more weight; additionally, arms on mechs will require much more engineering to pull the weight of the mech if the legs are knocked out. Tanks almost never need to be righted; they are spread over a larger area.
* Mechs are not tactical. 347
Tanks are lowlying and make only a grinding sound; with a mech, expect more height, more visibility from a distance, and a constant, ground-shaking thud with every step.
* Mechs will face recoil when shooting ammunition. When a tank shoots, it does not fly backward or collapse, as it is both low to the ground and spread over a large area. If your mech tries to match the shooting power of a tank, it will potentially fly backward, or at the very least, stumble and fall.
* Mechs require a large amount of energy to move at a fast speed, bipedally, to carry their weight. Meanwhile, the same amount of energy, used in a tank, would only need to power circular motion, or in an aircraft, engines - which is much more efficient.
* While mechs may be useful for engineering, this is modern warfare. Aside from building bridges, which can be done by less expensive manual labor with only slightly more time elapsed, they do not have practical uses in combat.
* Legs are vulnerable, and armor is trivial at best. As previously stated, just hitting a leg will effectively disable a mech in a combat situation. Even armoring legs leaves gaps at the joints, and any impact will potentially shatter or dislodge these joints; furthermore, the strongest armor will not stop a mech from falling over, even if it reduces some damage.
Mechs in Modern Warfare DO Have a Few Advantages
* They likely weigh less than tanks
* They may be reasonable if you do not need a large amount of firepower; i.e. somewhere between infantry and tank scale
In conclusion, mechs have a few advantages in modern warfare -- but they are far outweighed by the disadvantages.
I apologize for the coherence and/or validity of claims made in this post. It is 3:51 AM. 347