Is there a list of inbuilt parameters available to Sitecore XSLTs? I\'ve looked around but haven\'t seen anything that looks like a full list, at least not in comparison to the
Stating personal opinion, I think you should be grabbing the answer you already see right in front of you - forget about XSLT and just do C#. I don't know of many (in fact, any) seasoned Sitecore developers who stick with XSLT for anything but the most basic of renderings. This too, is of course, just my own personal view - but I've seen similar statements from many of the Sitecore bloggers out there.
And to answer your question, the drawback is complexity and development time. In writing your functionality, then writing and maintaining XSL helper libraries.