All of these bikes are vintage so the components would not be my main focus. I'd want to know about the frame, more than just double butted chromoly steel. I'd want to know if it's Tange, what level Prestige, Tange 1, Tange 2, Tange 900? It makes a difference. If it's another brand such as Columbus or Reynolds, again what level of quality. Then I'd pursue the components next. You might want to ask what size wheels are on these bikes. Are any of them 27 inch or are all three 700C. 27 inch is the sign of a lower end bike. I know for a fact the D-back is 700C, not sure about the others. Size is critical. It may be an optical illusion or frame design, but the D-back looks smaller than the other two. The wrong size frame is never a bargain, be sure the frame you choose fits you the best. Hope this helps.
EDIT: The guys that could really help answer your questions are over on the Classic & Vintage forum.