I don't know if there is a best. I think most ETL tools look similar how they visualize dataflows, and in what they do.
I think SAP BW is pretty good if you are an enterprise. Especially if you have a large SAP Landscape. Then extracting data is simple and fast.
Pro
I like their concept of infoobjects to organize the metadata.
I like the way you can schedule jobs and monitor these.
I like the programming features to customize SAP BW.
Cons
I do not like the GUI, but newer versions look more modern.
Licenses.
Expensive.
I think SAP BW is pretty good if you are an enterprise. Especially if you have a large SAP Landscape. Then extracting data is simple and fast.
Pro I like their concept of infoobjects to organize the metadata. I like the way you can schedule jobs and monitor these. I like the programming features to customize SAP BW.
Cons I do not like the GUI, but newer versions look more modern. Licenses. Expensive.