I do not know of any known issues with connection delays using the ODBC. Typically it is about the same time as the JDBC. May be you can turn on tracing on the driver or logging the ODBC driver manager to see what is going on. Also, you can place the Teiid server on Trace and see if the request is coming immediately or not.
Depending upon whether you are using Windows vs Linux the above configuration for tracing is different for the driver.
This is on windows environment. Is there a version of postgres odbc has been tested against teiid? I suspect it is the driver issue as jdbc connection is alot faster.
I have extensively used version 8.4.0200 version before. I used 9.x version once or twice. So, try 8.4 and see. On windows, you ODBC Driver manager you can turn on the ODBC logging as well driver traces. Note ODBC uses different port than JDBC, do you have restrictions setup on the this port on server may be?