If two vector are collinear and parallel and they also have the same magnitude then, it is necessary that they are equal vectors.
But If two vector are collinear and anti-parallel and they also have the same magnitude, then they are not equal vectors.
It is easier to use a unit like kilos when we are measuring smaller masses. But when we are calculating larger masses, it becomes more difficult to express something like 2000 Kilos, but it is much easier to say that the weight is 2 Metric tonne.
(As 1 Metric tonne =1000 kg)