For XSL Tools, you may consider Xselerator or XSL Designer/Debugger or XML CookTop;
XSL in general will perform badly for large files (as compared to small files); but carefully written XSLT on 50 meg file should not be an issue at all;
I have no comparision data with nodeIterator.
Other considerations before choosing either approach (apart from performance), should be maintainability!!
XSLT tends to be more complex.
HTH,
Saurabh
#Flow-and-Java-services#webMethods#Integration-Server-and-ESB