XSLT 2 vs XProc

I was reading through the XSLT 2 spec recently about some elements I  
wasn't familiar with.  The more I read, the more I became confused-- 
even though XProc was designed to fill a role that XSL did not—or a  
role that many people were trying to force XSL to fill—there is  
definitely still some overlap between some parts of XSLT 2 and XProc.

Has anybody sat down and compared the two?  For people who are using  
both XProc and XSLT 2 I would like to know:

anything that both can do, but is easier to do with XProc
anything that both can do, but is easier to do with XSL (if any)
anything that both can do, but XSL works better in situation A whereas  
XProc works better in situation B

—Tony