Thanks very much for all the responses.  It seems more developers are having experience with Netadvantage of Infragistics. (This is the idea we gather from the above posts and from other resources)
We were making comparison studies and found both DevExpress and Infragistics controls very much flexible.  BUT, one downside of Infragistics Netadvantage grid control was readily visible:  The grouping facility is slow compared to the Devexpress XtraGrid.  In this, XtraGrid is fast. Very fast.  We were checking with an ODBC  dataset containing 150,000 records.
But that alone does not make us take a decision yet.

Thank you all once again.