I have one of the six car sets. I model both modern military trains and WWII military trains. They look cool. The tanks are metal. They look good on the TTUX flats. What prompted me to buy a set in the 2007/2008 time frame was when I saw the actual Abrams tanks in Dagget, CA at the Marine Corp Depot on the way to Vegas. They were on TTUX cars. They looked cool in real life and look cool on the layout. Only a rivet counter would worry about the size of the tanks. They are very close to scale and you won't be disappointed. If you have a chance to buy a six car set grab it. I have both the desert and green camouflage tanks.
P.S: I like the Geller Military Loads also. But they are pricey. They are very detailed. My son bought me a couple for xmas a couple of years ago.