Tactical mobility: How well can it move under fire?
Operational mobility: How well can it get between battlefields?
Strategic mobility: How quickly can it get to battlefields?
Tracks vs wheels: Tracks are slower, more expensive, and less efficient, but can go over more difficult terrain.
Protection, in order of effectiveness:
- Avoid encounters with communications equipment and sensors.
- Avoid detection with stealth technologies.
- Avoid acquisition with jamming technologies, countermeasures, decoys.
- Avoid being hit with countermeasures or dodging if at all possible.
- Avoid penetration with armor/shielding.
- Avoid killing the tank or crews.
( #todo: The above is essentially the Survivability Onion Model )
Firepower: Usually a single very large cannon on a turret. Usually can fire a variety of munitions, granting flexibility. Auto-cannons are a close secondary option, trading firepower for fire rate and ammunition capacity.
Dual cannon tanks have proven to always be not worth the trade offs.
- Main battle tank: Jack of All Trades. Balanced between mobility, protection, firepower. Technically just defined by the most common design of an army. Depends primarily on intended use.
- Light tank: Fast, harassing, recon/scouting. Probably more realistic for interstellar control.
- Heavy tank: Sacrificing mobility for very heavy armor and arms. Usually this sacrifice is not worth it. (It's better to have two smaller tanks in almost all situations, and that armor is relatively easy to overcome.) Also super-heavy tanks.. are just even worse.
- Cruiser tank: Fast light tanks. If hover tanks exist, this is where they'd fit. Infantry support and breakthrough forces. (Don't use this category unless I'm using hover tanks.)
- Tank destroyer: More mobile, high firepower, low armor. Sometimes not turreted, sometimes with missiles instead of cannons. Typically low profile, designed to sneakily hunt tanks.
- Self-propelled anti-air/artillery: Easier to move, high firepower, decent mobility, low protection.
- Assault gun: Direct support of infantry from a higher and farther position. Decent firepower and mobility, less protection - primarily intended against targets infantry can also attack.
- Infantry fighting vehicle: Basically an APC that is armored and armed so it can stay with the infantry force in a support role. Carries less troops and may be slower than an APC for this reason.