If you want a balanced set of opinions, ask the same question over at Coltforum.com, and watch the fireworks. lol
Colt and Smith & Wesson are both fine old American premium gun brands. Which one is best? Is Chevy better than Ford? Of course.
Diamondback values are escalating at phenominal rates now. The value depends on many factors.
What caliber is it? What barrel length? What finish? Which stocks? How rare is this configuaration? Do you have the box and accessories and papers? Serial number range? The financial value of the gun depends upon all of these factors. PHOTOS! We need photos! Detailed, closeup, macro-lens high definition photos of all parts of the gun. Condition, Condition, Condition. Nobody can accurately assess your Colt or your S&W without that information.
With that information, the helpful experts here and, for the Colt, at Coltforum.com (many frequent both Coltforum.com and Smith-Wessonforum.com), will be happy to tell you anything you want to know about your fine guns.