SAP Migrations are never easy. This week I created a long post about how it is possible to make a good SAP PI to PO migration.
The purpose is to go from a dual stack to a single stack.
The reason you want to migrate is that it will make your SAP landscape much simpler. The java only instance is easier to maintain because there is just one server to run.
Performance is also better because of the java only, so there everything can happen in the same transaction and be processed fast. In the dual-stack you needed to move messages between the ABAP and JAVA stack up to 4 times per message, so there is room for improvement.
And then the big point is that you will be able to get maintenance of the system. SAP has reported that no more development will happen for the dual stack systems.
Read more about how to migrate from SAP dualstack XI/PI to a PO single stack system here.