xmlWriterare very fast, given that they are little more than wrappers for direct reading/writing that process extra information, or add extra information, respectively. The amount of time to open a handle XML data is constant, as it is not affected by the size of the XML data.
xmlTree, the entire XML document needs to be read and parsed before any operations can be performed on it, so it is affected by the size of the XML data. The
xmlTreeAPI is very fast for an XML parser, but there will still be a noticeable delay when parsing 900MB of XML data, for example.