Generally, it's easier to add attributes than add elements. So from this perspective, using text is probably safer than using attributes. You can always add another attribute to the text's element. Good Use of Text UDDI uses text and attributes in a compelling fashion in which the difference between text and attributes is clear, logical, and consistent. Conclusion Attributes make a lot of sense to me.
Attributes are easier to create and process via the most popular APIs.
Attributes reduce document size compared to text. However, if you want to use the NULL and in-line typing features provided by w3c schemas, you must use text. There is an unfortunate bias towards element text throughout the XML community. Turning a data value into an element will break any existing code. This is true regardless of whether attributes or text is used.