By "stylesheets", do you mean XSLT or XSL-FO or FOSI? If you are talking FOSI or FO for output, and Epic Editor is your normal editing and output source, it is probably better to use Styler, which is more closely coupled to Epic. You would be able to better and more quickly see the results of your efforts. For the same reasons, if you are talking XSLT, I like to use XML Spy, another Altova product. I don't know anything about Stylevision, but if it is similar to XML Spy, it might be better for XSLT. XML Spy allows for the immediate gratification of your XSLT editing efforts. However, like I said, I don't know anything about Stylevision.