xsl data type problem? two values appear to be equal b

Here is the opening part of the problem template:
--------------    
<xsl:template match="data-store[@id=$node-id]">    
    <node type="{local-name(.)}" id="{@id}" name="{name}">
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This selects the node I expect. So far, so good.
Now, further along in the template I pass a parameter to a called template:

<xsl:with-param name="ds-predecessor" select="/fssc/component-list/processes/process[data-sinks/data-sink[.=$node-id]]" />

This works, too, but if I define the parameter in this way, no nodes are passed:

<xsl:with-param name="ds-predecessor" select="/fssc/component-list/processes/process[data-sinks/data-sink[.=@id]]" />

The 'match' treats these two values as the same, but the 'select' seems to treat them differently.I have output both values using 'xsl:value-of' and they seem the same.  

I also used the compare() function on the two and got a return value of '0'.My hypothesis is that they must be of different data types and that's why the called template behaves differently when called with one or the other. 

I have been searching the index of XPath 2.0 Programmer's Reference looking for a function that will return the data type of a node or variable passed to it, but I must have the wrong idea of what I'm looking for, because I can't find one.

Will someone kindly tell me why these two are the same and different? Thanks.

-- 
Charles Knell
cknell@xxxxxxxxxx - email