High reps with lighter weights vs low reps with heavy weights. Which one is better?

One who have studied or understands  human bio-mechanics can easily explain the concerned topic that is what should be preferred between light weights with high numbers of reps or heavy weights with low reps.

First of all, discussing about light weight with high reps, it consists of repetitive actions that means we perform a particular exercise or set with a increased number of repetitions and keeping weights lighter. Hence performing this type of training leads to increase in repetitive strength, for the works in which we perform repetitive processes or actions. It consists of 12 to 20 reps in a single set. This type of training is highly beneficial for athletes, runners , etc. In light weight with high reps training our strength increases but our maximum strength cannot be identified. It also results in certain change in muscle fibres.

Secondly, if we talk about training which includes heavy weights with low reps, it includes lifting of heavy loads with an average repetitions of around 6 to 10 reps in a single set. It involves short time muscle engagement and is beneficial for works which promotes short time use of muscle but includes full strength, for example, sprinters. Heavy weight low reps training helps in increasing the buffering capacity of a person. It also helps in increasing the ion transport system in human body.

Now, it depends on your goal, which type should be preferred. 

If your goal is fat loss and strength development then mix up of both would be very useful.