Argument Versus Opinion.
As indicated above, the key difference between academic and personal writing is that whilst the first should always present an argument, the second is more likely to express an opinion.
An argument involves arriving at a judgement which is based on an evaluation of relevant ideas and evidence.
An opinion, on the other hand, is a point of view formed without sufficient evidence to support it. It tends to reflect an individual's instinctive reactions and personal experience.
Consider, for instance, the difference between the following:
Children who have seen violence at home repeat it when they grow up - a friend of mine from school whose father was violent is now in prison for attacking someone during a night out.
International studies of sizeable prison populations demonstrate that significant numbers of violent offenders have witnessed violence in the home as children, though the influence of other environmental, and genetic, factors must also be considered.