This is probably a good candidate for moving over to the regular PX/EE forum.
...a lot depends on what "kind" of EDI we're talking about. Legacy EDI, like SWIFT and EDI X12 or other standards, are best handled by tooling such as WebSphere TX, which comes with built in metadata mappings (called Type Trees) as part of their subscription. At one time there was a MapStage, which supports communication between WebSphere TX and DataStage, but it doesn't exist anymore, as the two can be connected via Java Integration Stage if necessary. If using the newer formats that are largely xml, TX is still a good choice because many of the mappings are already built for the standard, but the xml Stage in DataStage is capable of reading and writing.
Choosing one vs the other will depend on many factors, such as the available skill sets, the numbers of such interfaces you need to build, the nature of the targets (is this source EDI and target EDI, or source EDI to data warehouse, or data warehouse to EDI, etc.), the performance you need, the transactionality you need, etc.