Comparisons

Sebastian Rahtz

 - XT is best because its the fastest
 - Saxon is best because it implements all the spec
 - Oracle is best because it has a C version alongside (incomplete)
 - Xalan is best because it it is politically correct (in Apache)
 - Microsoft is best 'cos its in the browser

If Michael Kay's reported optimization changes in Saxon live
up to expectations (ie it reaches the approximate speed of
XT), I for one plan to switch to it from XT. Perhaps a
downside (or strength, depending on your view) is that it
has a single author who does it for "fun".[1] The fact that
James Clark seems to have gone entirely quiet with xt (ie it
is still incomplete vis-a-vis the spec) shows the problem
with that.

If Microsoft release a version of their XSLT which 100%
implements the spec, of course the picture changes
dramatically.