Why do you again try to manipulate comparison ? To make your point of view about protection (you do not want to show big weak zones in Leopard so you manipulated) you compare simple T-72B while it was clear it is T-72B model 1989 level (T-72BA) with Kontakt-V ERA, of course you eluded. So far nothing valid.
And your calculations about weak zone protection are funny, because even if those values are correct (I believe), they are poor for today's standarts. Exactly the same applies to T-72 with late 80s level protection. What is the point of making wonders out of outdated material ? (you focus on making protection look decent, but it is aknowledged that it is just outdated level today no matter if there is difference of 50, 100 200mm or etc. it is not relevant in today's context).
You make first mistake
Soviet composite armors during cold war were inferior to Burlington in term of protection.
First thing is used materials.
As we could see, Soviet composite armors are mostly based on one single base material, be it alluminium filler in Combination K, T-72B's simple steel plates with rubber, or cellural casting of T-80U with polimer filler.
While Burlington armor, was modular design, easy to be modified per needs.
In documents there are even mentions about Burlington variant with build in explosive reactive armor.
But the basic design is also interesting, because NERA array wasn't nothing new, but how materials used in this array were combined. Especially later types of armor that were based on Burlington design.
The most interesting applications is to combine different armor steel types with heavy metal alloys.
Thus by combining high density depleted uranium or tungsten alloys, encased in semi hardness, high hardness or triple hardness steel plates, we can achieve increase in both KE and CE protection. Also take a note that this is still a NERA like array using such protection mechanisms like yaw, bending and a working mechanism called by Burlington designers as "whistle effect", what is this and what are principles of this working mechanism, are unknown.
Another problem with soviet tanks were their turrets. Russians sources says that cast turret armor is from 5 to 15 % weaker than it's rolled analog. What type of turrets have soviet tanks back then? Of course cast, while NATO tanks with composite armors, have turrets made by welding steel plates.
Another problem of soviet tanks is space used for composite armor per complete thickness of armor array.
When we compare how much composite filler is used in Soviet and NATO designs, we can observe that NATO designs at any predictible hit angle, have more composite armor standing against incoming projectile than soviet designs.
When we combine all of these characteristics, compare them, we can assume that NATO found a way to develop more advanced composite armor... of course the price for that was more bulky and heavier tank design.
But what is important, Burlington armor design evolved whole time during cold war. Of course, some people from some countries (vide Lidsky) will try to argue with reality, but the fact is that Leopard 2A4 manufactured during second half of 1980's, or M1A1HA manufactured in the same years, still have descent protection.
Not new manufactured does not mean completely obsolete.
There are of course many more factors, like ease of armor replacement and modernization, etc.
I had interesting conversation with a person from Kharkiv, I asked him if it is possible to replace composite armor in soviet tanks with cast turrets. He only confirmed the very well known fact in my country. In many soviet tank designs, turret armor replacement might end with significant structure damage, thus armor replacement or even repair might be difficult or immposible.
While in NATO tanks, not matters what variant, might have armor replaced with ease. American maintnance teams before Operation Desert Storm were able to replace armor in older M1A1's in 30 minutes spent on each tank, thus simply upgrading them in to M1A1HA standard.
This shows that without changing vehicle base standard, and without significant external difference, protection of NATO tanks might be improved without significant costs increase and time increase.
And Damian, do not spend time now searching for information on russian forums, it just confirmed how ignorant you was in subject and discussed only with empty words, but it was clear for me already.
I asked people that know more about this, and guess what, they proved my point and what I said.
http://vadimvswar.narod.ru/ALL_OUT/TiVOut0809/T-72BA/T-72BA001.htm
Good source, it shows that T-72BA is not a single standard. Some T-72BA do not have even thermal sights, but old active IR night sights.
Simple refurbishment, not a real modernization, hard to be comparable even with older variants of NATO 3rd generation MBT's.
typical 
