We have to be careful when we want to encode a multiple solutions in a variable length chromosome (for instance in a standard GP chromosome), because this kind of chromosome will tend to increase its size in order to encode more and more solutions. And this could lead to bloat...
MEP introduced a unique feature: the ability to encode multiple solutions in the same chromosome. This means that we can explore much more from the search space compared to other techniques which encode a single solution in the chromosome. In most cases this advantage comes with no penalty regarding the running time or the involved resources.