Well we really dont know for all it could be for the same weight they may offer better protection like ERA.ERA & Both composite Armour are evolving, But in case of composite Armour the weight is increasing but not the same..
Behind the ERA there is still the armour to deal with , so if a composite armour takes double shot then it would still be bad and ERA and Composite armour takes a double shot it still is bad.....there is no difference between two.What i told ERA cannot tank a double shot on its surface unlike main Composite Armour..
Bigger Engine means higher fuel consumption.Put a bigger engine, Wider tracks and have all tactical equipment to support it..
Wider Tracks means if the area is mined you are more vulnerable compared to smaller track for same area , plus now you need more power to move as you are exposed to more area on ground.
If Wider Track was the solution for all things ground pressure then we would have seen wide use of such tracks in Western and Eastern system.
Some one would argue even a 70 T is too much ....there is no fix rule for weightIn that sense yes 100 ton will have more protection, But that is to much for this era..