Replies

If I remember correctly,
the Leopard II, the Chieftan (or is the latest Brit tank the Challenger, I forget) and the Abrams all went into production about the same time.

All three use the Chobham composite armor. The trade off in armor is generally protection versus mobility. The more armor you have... the less agile the tank is (and the fewer bridges that can handle the additional weight).
The Germans went with mobility... it's the lightest of the three. The British tank Chieftain (or Challenger) and the Abrams have more armor... and I guess if you're a tank crewman... there's no such thing as too much crew protection (they're sort of like Volvo drivers in that way).
Interestingly, the Brits and the US used slope armor which helps deflect ballistic hits, while the Germans put their armor in vertical panels. I guess they had the most confidence in the newfangled Chobham composite armor.

Of those three I don't know which is the most mechanically reliable. I do know that the gas turbine engine (IIRC, the Krauts and the Brits stuck with the Diesel)on an Abrams needs a lot of fuel to keep rolling.

The Israelis developed the Merkava independently (though the Israelis wanted to bid on the M-1 project, but we didn't want to share the Chobham ctechnology with them). The Israelis developed their own composite armor and they put their engine up front. More steel between a round coming from 12 'clock and the crew.

The Leopard II has never seen combat and probably never will. I don't know enough about the Israeli track record with the Merkava to compare it to the British or American tank. However, I am familiar with British craftsmanship (my dad used to own a Jaguar which led to him pretty much putting the mechanic's kid through college), so I'd go with the Abrams.