reason for rig my character with Metahuman topology?

Good topology

Character artists may occasionally ask such a question: “How should I design the modeling topology?” Surprisingly, the answer to this question is quite simple: Structure the topology to be easy to create and deform without any issues.

True, while ensuring ease of creation and deformation, maintaining the aesthetic shape of your character can indeed be challenging. The answer to the question may be simple, but satisfying all three conditions simultaneously can be quite demanding.

Therefore, for bipedal or quadrupedal human or animal characters, there are generally established topologies that offer a certain degree of deformability and shape integrity, commonly used across different projects. For instance, the base mesh in the DAZ Studio Gen series is a good example of such a topology.
Here is official DAZ3d Site

then, what about MetaHuman topology?

compatibility

The most fundamental reason is the resource compatibility between multiple characters created with MetaHuman. When both the body and face are rigged to MetaHuman topology, all textures, UVs, vertex counts, IDs, etc., are matched. This makes it extremely easy for future modifications, enhancements, or texturing using blend shapes, and it becomes very convenient to use various services that support MetaHuman

Of course, these advantages are not structurally different from other similar base topologies. However, MetaHuman topology has clearly distinguishable stages at each LOD level. This plays a crucial role in render optimization, and if the LOD models themselves have consistency with unified characters at each level, it can enhance resource optimization, uniformity, and manageability.

base topol for future

As an artist, aligning clothing creation or models based on the base topology is one of the most basic and important settings for a character and serves as a foundation for all future workflows.

If all your characters are converted to MetaHuman topology, not only your current characters but also future character development can benefit from it as a resource. Efforts to develop your characters consistently now will likely establish an important pipeline for saving time and costs in future development.