My favorite MBT is the Israeli Merkava when it is also an IFV. The Leo2 is a great tank, but as what you said, Monty. It has been around for awhile now.
I think everybody who have purchased Russian tanks regret it now, but the design flaw of the Russian tanks (T-64, T72, T-80, and the T-90) have been known since the early 1980s when the Israeli forces clashed with Syrian forces in Lebanon. The wars in Chechnya, Georgia, the first Gulf War and the second Gulf War confirms the problems with the Russian tanks.
Is the T-14 Armata better than the other Russian tanks? Maybe, I don't know, but they will have a huge problem to sell their stuff. Another problem is how the Russians are using their tanks and other vehicles. I really questioning the Russian military training based on how they are operating.