JAXTHelper vs LibXSLTTransformer, which one is preferred?

Hi,

I'm developing an document import filter (which will be packaged as
an .oxt extension) and it needs to perform XSLT transformations during
the process of importing (I don't believe xsltfilter could cover these
process). So I'm finding a way to use XSLT transformation services
directly.

In libreoffice 3.5.4, which I'm working with, there seem 2 UNO service,
i.e., com.sun.star.comp.JAXTHelper and
com.sun.star.comp.documentconversion.LibXSLTTransformer.

Currently I'm using the later one (by specifiying its service name in
the ServiceManager.createInstanceWithContext()), but both are just
working fine for me. So here are my questions:

1. Which one is preferred to be used in regard to forward/backward
compatibility? It looks like LibXSLTTransformer is introduced later,
then will JAXTHelper be deprecated at some point in the future?

2. Or should I choose one of them conditionally according to the version
of the Libreoffice installation? If this is the case, from what version
should I use LibXSLTTransformer?

3. Or direct instantiation and use of them like these (not through
xsltfilter), is unsupported and discouraged way?

Any guidance or comments would be greatly appreciated.

Best regards,
mete0r