I was a SSIS developer and very new to this SAP environment. There are lots of cons and pros using SAP. I can say I am a export SSIS programmer but I still need to learn lot of SAP environment. One thing for sure SAP has very limited support community unlike SSIS. There are tons of tutorial, books for SSIS. One thing for sure, SAP has very poor documentation and it's DS interface is not very intuitive. SSIS visual design interface by far the best in the market and it works extremely well for debugging.
As I said I am very beginner to this SAP world and can't talk much about SAP performance but I didn't like it's DS tool.