Really you shouldn't be just doing just one. It of course depends on the situation, but i would use a jab as a distraction followed with power hand strike. Thats the kind of basic move that demonstrates using easy speed that requires little effort followed by a power strike using the body. I wouldn't spend the duration of the encounter trying to tap him with lightning fast punches, nor would i do body power strikes that require a little more technique to do the entire time. It has to be a mix of both in my opinion. Lead jab followed by power hand is the most basic example of this. Jab as a distraction and power strike to finish.

Well think about it like this would you rather hit somebody with 10 fast punches and overwhelm them and possibly knock them out not giving a chance to defend themselves or throw 4or5 slow ones and maybe knock them out but risk the chance of u getting hit ... Try boxing if u really wanna get good with your hands

...in order for point A to connect to point B, point A needs to travel towards point B first. Therefore the most important aspect in fighting is not dealing damage, its how to put yourself in an optimum position to deal damage. The one with the better footwork will win because he will know how to gauge and use his punches accordingly. Just look at Manny and Floyd boxing style...beautiful footwork.

Focus only on punching , what would you pick if you had a chance, fast punches? Or powerful punches? And after you pick one, you gotta fight the opposite of what u picked... Me personally , i wud go for powerful punches in a strreet fight...