They were generally considered to be more fair than sword duels. Skill with the sword was such an advantage in duels, that a skilled fencer could get a reputation for being a murderer merely for accepting a challenge to fight with swords, unless his opponent was agreed to be an even match.
Pistols levelled the playing field, somewhat. Yes, you could practice at shooting until you were a crack shot, but duelling pistols were finicky and inaccurate, so becoming a perfect shot generally meant practicing with a particular set of pistols to learn their "throw" -- but that was widely considered to be poor form, akin to cheating, and once again you would be tempting a reputation for murderousness if word got around.
Shooting deliberately (with intent to hit) but not too deliberately (taking long and careful aim) with a pistol you weren't too well practiced with was good duelling etiquette. This sufficed to introduce an element of chance into the affair that was commonly felt to improve the impression of fairness.
There were many conventions for how to conduct pistol duels, and not all of them involved reaction times. For instance, the duellists might take aim prior, so that they could both pull the trigger simultaneously on the signal to fire. Or, they might draw lots to determine who fires first, and the other would simply stand and receive their fire before being allowed to return fire. Again, these conventions were intended to increase fairness by increasing the role of chance, and reducing the role of skill in the outcome. (Incidentally, the movie Barry Lyndon illustrates both of these pistol duelling conventions in the two pistol duels that bookend the movie.) If your sense of fairness was to maximize the chance of death, rather than randomize it, there was always the duel au mouchoir, in which both duellists held the corner of a handkerchief and fired from that distance.