No, they are neither more accurate nor higher quality. They are discontinued, which boosts their value as in supply-and-demand. And, as the premier manufacturer of revolvers, the name "Colt" just has charisma, what the appraisers call "provenance." Also, the Single Actioon Army, because of its association with the old west, carries a premium. In a similar vein, Winchester carries the same value.
Both Colt and Smith & Wesson were, and for Smith, are, examples of the highest quality.