A common question in martial arts circles is what styles are superior in a street fight. In many cases, it's an "apples and oranges" argument, such as comparing a ground fighting arts, such as wrestling against a stand up art like karate. Kickboxing and boxing are very similar, however, and a comparison between them makes more sense than many others.
Boxing and kickboxing share many advantages when it comes to a street altercation. Both provide fighters with tools and strategies to use if attacked. Both include rigorous physical training to make attacks hit harder and to help the athlete absorb damage. Perhaps most important, as defensive tactics instructor Lee Sprague points out, boxers and kickboxers spend time getting hit. That means the blows they receive in a fight won't make them panic.
The shared disadvantages of kickboxing and boxing stem from the fact that both are practiced as sports. Sports follow rules, and rules don't exist in street defense situations. For example, kicks to the groin, although very common in a street fight, aren't allowed in boxing or kickboxing. Thus neither teaches how to deliver or defend against one. Similarly, neither style deals with eye gouging, biting, attacks to the throat or any kind of ground defense.
The chief advantage kickboxing has over boxing is its range of tools. Kickboxers train their hands, feet, elbow, knees and sometimes heads as weapons for striking. Not only do they learn how to use those weapons, but they also learn how to defend against them. As Joe Lansdale put it describing an altercation with a boxer, "He was pretty good, but I had four wheel drive."
Where kickboxing teaches a range of tools, boxing specializes in one thing and one thing only: punches. A skilled boxer punches so well that boxing was the only western martial art to impress Bruce Lee enough to include its concepts in his martial art Jeet Kun Do. Boxers also tend to be faster than kickboxers, again owing to the necessity of defending against the lightning fast jabs or their training partners.
Importance of Context
There is no such thing as a superior martial style, according to martial arts instructor Dave Coffman. There are superior athletes, superior coaches and superior methods of training. A dedicated, talented kickboxer with a skilled coach will beat a mediocre or unmotivated boxer, and vice versa. Between two equally talented athletes, one a boxer and one a kickboxer? Coffman says "it will boil down to who wants it the most on that particular day".