This is a little comparison between XPath and DOM. I hope this will help you to determine which method is better suited for your situation.
Complexity: XPath is much simpler that DOM. XPath can also be used in SQL directly while DOM you must write a stored procedure.
Flexibility: DOM is much flexible than XPath. You can read an entire XML document without knowing any specifics about the document upfront. In XPath, knowledge of the document design is required.
Speed: In our test on 126.96.36.199 on Linux, DOM was 3 times as fast as XPath when parsing 500,000 XML documents.