The Soviet Stronk Tenks include the only Tier 4 vehicle able to bounce AMX-10P PAC 90 HEAT rounds, the T-64. T-62 and T-64 are pretty good, T-72 Ural and T-72A underperform a little (literally; their engine performance lacks, and so does their armor a bit), rest of the line's average.
High-Caliber Light Armor's pretty fun all the way through, with the Bagelpanzer being a definite high point; the Stingrays are still fun but an obvious low in comparison to that or other vehicles their tier (the preorder Expeditionary Tank is clearly superior), but the XM8/M8 are excellent.
BMD line is like playing BMPs, only low profile and SUDDENLY A BRADLEY, plus it caps out in Terminatorville, which is always a good place to be.