lets go with merkava tank development to get an insight developmental stages
Date of service:
Merkava I -- 1979
Merkava II -- 1983
-Merkava III -- 1987
Merkava IV --2004
Country: Israel
Type: Main Battle Tank
Dimensions: Length, 7.5 m (22.4 ft); width, 3.7 m (12.2 ft); height, 2.75 m (9 ft)
Combat weight:
Merkava I -- 60 tonns
Merkava II -- 63 tonnes
Merkava III -- 65 tonnes (140,000 lb)
Merkava IV --- Classified according to wiki 65 tonns
Engine:
Merkava I -- Teledyne Continental V-12 diesel 900 hp
Merkava II -- Teledyne Continental V-12 diesel 1,200 hp
Merkava III -- Unknown, believed to be 1,400 to 1,500 hp
Merkava IV -- Unknown
Armament:
Merkava I -- One 105 mm M68, rifled
Merkava II -- One 105 mm M68, rifled
Merkava III -- One 120 mm smoothbore MG251 smoothbore tank gun
Merkava IV -- One 120 mm smoothbore MG253 smoothbore tank gun
All Models -- Three 7.62 mm NATO machine guns;
one 60 mm mortar
Crew: 4
Speed: 46 km/h (28.6 mph)
Range: 400 km (249 mi)
Obstacle/grade performance: 0.95 m (3.1 ft)
Combining the best features of American, British, French, and captured Soviet tanks, all of which have been used extensively by Israel in the past, the Merkava is the product of real battlefield experience. The 1967 War, which spurred the development of the Merkava as part of a native Israeli defense industry, demonstrated the extreme importance of armor protection to such an extent that the Merkava's design emphasizes tank survivability, armament, and speed in that order.
conclusion most of the western tanks gave importance to primarily to tank survivability, armament, then comes speed in that order. there are no signs of decrease in weight even Abrams, Lepord etal