SAP EP (Enterprise Portal) and XI (eXchange infrastructure) are subsets of cross-component BPM (business process management) in which processes flow across multiple application modules. Because XI is used to support trading partners and mapping of disparate processes and data conventions, it tends to be more challenging from an analysis perspective. EP deals more with internal processes, and it is used to empower users (especially expert users) to implement process improvement. If you are more of a business process analyst, then perhaps the BPM/EP track is more appropriate, while if you have expertise in working with trading partners BPM/XI might be more appropriate. A third option (e.g., if you are more a Basis person) is learning the underlying Netweaver capabilities – e.g., message management, alarms, etc.