Dodge RAM 3500 vs. Ford F350

Hi together, interest me a little bit for the big Ami pick-ups. Especially the Dodge RAM 3500 dual with the 5,9l cummins and 6-speed did it to me. But also the Ford F350 dual with 7,3 V8 or with 6,6 duramax has what. Everything as diesel minded !! Now my question to you: What should I consider when buying such a car ?? Have no experiences in this sector and would be happy about qualified attributions. What about the quality, with how much KM is worth The purchase of such a car ??? prefers to buy in BRD or import it yourself ?? theme consumption, are 15l realistic ??? What about insurance and tax ?? Are there alternatives to these cars ?? which can also be obtained with diesel and hand-operated ?? So for the first time these are probably enough questions, I am happy about every attribution. Greeting @ all Scan