What is better for Index performance? Structure of XML Elements or Attributes?

Question

I am using Oracle Binary XML and will be creating XML Index. What choose structure of the XML file for better search performance? XML Elements or Attributes? For example:

a) Attributes style

<tools>
    <tool number="09201-10000" />
    <name>Valve Guide Bushing Remover & Replacer Set</name>
</tool>

vs

b) Elements style

<tools>
    <number>09201-10000</number>
    <name>Valve Guide Bushing Remover & Replacer Set</name>
</tool>

I will look for "09201-10000"

P.S. Oracle has three types of XML indexing. Function-Based Indexes, Oracle text and XML text. What is better and why?