again rarity or obtainable doesnt matter when u talk about the best vehicle.
And the armor of the moderan is better as the one of the leopard, its smaller as well
Heck even your T-72B (1989)has the better frontal armor then the leopard
leopards good aspect realy only is mobility and turret traverse.
In brawling several vehicles are just way better
you are talking like mobility is king, but at that point m113 cv90105 are better then leopard 2a4s
Mobility aint everything
The question about the best is hard, i cant pinpoint it clearly either, but its not the 2a4 like you so seemingly seem to declare when it gets outmatched in several aspects across the board easily
this picture is all that needs to be said about its surviveability, shoot at it with dm23. just shoot at the left hull, everyones conveniently lined up to get taken out at once