Traditional tank design has to balance firepower, protection and mobility. There is usually a trade-off between these three, as two increase weight and the third deteriorates somewhat with weight.
Good reliability and durability, low supply demands, good range, low maintenance and quick repair are important hidden values which require little trade-off.
|T-34: It was the first properly balanced tank, but weak on 'hidden' values.|
Many Chobham-generation main battle tanks (beginning with Leopard 2, ending with Merkava IV and Leclerq) got the balance about right, as "Chobham"-like armour finally offered good protection at acceptable weight.
The German 1990's upgrades to Leopard 2 increased frontal turret protection and firepower, whereas later upgrades increased mine protection. Other countries limited their upgrades even more, increasing firepower only through improved munitions.
Much money was also spent on better sensors and electronics.
The 1999 Kosovo Air War and subsequent U.S.Army panic about "relevance" and "deployability" pushed deployability (low weight) to the foreground and AFV development focused on this frantically for a few years. The Iraq War 2003+ shifted the emphasis to electronic countermeasures, roadside and underbelly blast (and EFP) mine protection, but most AFV projects were still relatively modest-weight wheeled vehicles because tracked vehicles couldn't run the same thousands of kilometres every year, much less at the same cruise speed.
Now - after a decade of occupations - the emphasis still seems to be on protection, with very little emphasis on firepower (especially not high-end anti-armour firepower) and mobility concerns are still about cruising on highways or air lift rather than off-road manoeuvres.
The confusion about the American FCS and GCV projects with radically changing protection and mobility demands suggests a certain cluelessness or maybe rather uncertainty:
The meaning of "balanced" is in question. What's a balanced tank (or AFV) design in regard to firepower, protection and mobility nowadays?
Judging by military history, I guess a later generation may find the present emphasis on protection and road mobility exaggerated and may complain about (anti-tank) firepower and offroad (soft soil) mobility shortcomings.