There is a difference between the two. The former is the result of careful thought and analysis while the latter is due to the fight-or-flight inbuilt mechanism deeply rooted in our genes.
Response is always better than reaction. Because it is more human. Thousands of years of evolution laid the foundation for a species to respond and not react to external stimuli. Think about a deer grazing blissfully on the green grass top of a dense Amazon Forest. The moment it hears the marching footsteps of a lion - it immediately springs hard and runs as fast as it can. This whole fight-or-flight feedback is instantaneous and doesn't even reach the brain - its a nervous system response - much like the way we react suddenly upon touching a hot iron rod. This is called reflex action. Reflex action was good - because it was designed to save a deer or a man from the hungry mouth of a lion... But reflex action alone is not so good... mix it with careful analysis, observation and thought - and it becomes a lethal weapon. And that's what happened to man... being frustrated from the attacks of lions, man started thinking of better ways to tackle the problem - so he invented tools - with which he could now attack or scare away the animal.
Homo-sapiens sit on the topmost place of the food chain in-spite of having a weak physical defense and comparatively lesser strength, due to the gift of a unique brain which is capable of out-smarting its competitors quite easily. Other species stand simply no chance against us. So today if there is any enemy of a man, it is none other than his own fellow being. He has no one else to fear from. You might see two bulls or two lions fighting with each other in a National Geographic Channel - but seldom are these 'fights till death'... no sooner does one sense defeat it backs off and runs hard to save it's life. But one man brings death to another quite often with careful planning, observation and analysis and sometimes without any reason or on spur of the moment... This is quite strange. The gamut of emotion that man is capable of exhibiting - starting from extreme love at one end of the spectrum to uncanny hatred at the other end is quite phenomenal.
There is no doubt in the fact that man is different from all the other species in his ability to think and analyze using his brain. Such a brain no other living entity has... Over a period of time it has been the ability to respond (and not just react voluntarily) to a particular crisis or a problem which has allowed him to survive.
However since evolution is a continuous phenomenon, so the fine tuning of human attitude is still continuing. The same external stimuli creates different kind of responses and reactions in different human beings. Let us try to plot a chart - with A being the most perfect hypothetical human being (or an Angel) and D being the most imperfect:
|A (the hypothetical perfect human being)||0 %||100%|
|B||60 %||40 %|
|C||70 %||30 %|
|D (the most imperfect human being)||100 %||0 %|
We can say degree of being a human being in case of B is more than C. If we carefully look into the lives of B and C, we might find that B is smarter that C. I might go one step ahead in declaring that degree of success, fame, prosperity and other positive rewards is directly proportional to this degree of being a human. In other words the more one is closer to A - the better it is for him.
Losing temper and lashing out at someone with anger and venom is nothing but reaction. This is a behavior that leans towards row D - which is the zone that belongs to animals.
You would have seen someone who loses temper and does something stupid, repents later, because moments after slipping from the human zone, he comes back into it and then starts thinking. It is only that situation was not in his control. Another person might behave differently when faced with exactly same situation. The feelings of anger might rise in him as well but he knows the art of controlling them them and choosing to react in another way which is both effective as well as witty. Each time a bad external stimulus tries to knock you off... you can just hang in there, trying to observe the whole chain of thoughts and feelings very minutely and then trying to remain in conversation with others - choose the right words and sentences with logic and with calmness. This will clear the cobwebs of confusion and you can continue to be in control.
This holds true for most of the cases - picture yourself in middle of a shopping center - and your kid is throwing strong tantrums and it's a very difficult situation to control. Already your kid is reacting to a certain unfavorable situation - and if being a parent you react back at his tantrums - then the situation turns ugly. Rather if you can engage in calm and assured conversation and make him understand properly about the message you want to convey - then things might turn out better.
There will be a lot of pleasantness around one when he has mastered the art of controlling the situation by being responsive. It is not very difficult - and can be easily honed with perseverance and practice. One has to remain in a state of awareness and proactively not try to be impulsive and try only to be logical and normal as much as one can. A genuine and assured smile often helps in such situations.