Arjun, Leopard 2, Challenger and Abram do not have auto loader. They need to make the tank bigger to accommodate the loader crew. Therefore its heavier but doesnt mean thicker or better armour than auto loader tank which weights 48-56 tons.
Japanese type 10 and Type 99A and VT-4 are all auto loader tanks.. 40 tons vs 56 tons vs 54 tons. You do the maths and see which is better.
Ammo storage is also separated from crew in modern NATO standard tanks including Abrams. This design contributes to turret size but also enhances safety of the crew.
NATO standard tanks are heavily armored on average because Western countries tend to value protection over sheer numbers in this matter. British and Americans in particular although the latter have numbers as well.
This is authentic information:
The afore-stated levels of protection are PLAIN BODY only (ERA and the sort excluded), and established against two different types of (modern) rounds that are optimized to penetrate very high levels of body armor from good distance. You can notice how those figures vary for one type of round to another type of round. ERA and the sort will enhance those figures subject to where they are applied.
The latest M1A2
C is relatively better protected and heavier than the M1A2 SEP (considering PLAIN BODY only) - classified information nevertheless. Word is that the M1A2
C is the most heavily armored tank in the world in the present.
Americans are developing another variant of Abrams as well which will be a substantial leap from the already very impressive M1A2
C. Imagine this.
Therefore, gross tonnage can be a predictor of protection levels in tanks that are of the same generation or fielded in the span of one decade. Now which country is developing the tanks in question and how it is marketed in potential disclosures - these are important considerations as well.
Heavier does not mean better armor. Maus was 188 tons.
en.wikipedia.org
Potential comparisons should be (logically) with same generation of tanks fielded around the world in the span of one decade, and not across different generations of tanks rolled out over a span of century. Body armor advances should be accounted for, and industrial bases of relevant countries can be predictors in this regard.
Maus was better protected than
Tiger II which in turn was better protected than any other in times of World War II. Therefore, gross tonnage can be a predictor of protection levels in tanks that are of the same generation or fielded in the span of one decade. Of-course, industrial capacity and experience of the developer is also instructive in this matter.