CHAR() v. VARCHAR()

We are using Informix 7.01. We are using PowerBuilder for developing client/server applications. PowerBuilder does not strip the padding off of the CHAR columns when rows are added to a DataWindow. Our DBA claims that VARCHAR() is much less efficient than CHAR(). Yet, he claims that both are fixed length columns with null terminated string data. He claims that Informix pads the CHAR() columns either at the time of the SELECT or at the time of transmission to the client. If both are null terminated strings in storage and the CHAR() is padded when retrieved, why would CHAR be more efficient for storage of string data. It would seem that padding the data at the time of retrieval would make CHAR() less efficient re. server resources than VARCHAR(). I can appreciate that most SQL servers store VARCHAR() data less efficiently than CHAR() data but VARCHAR() has a very different meaning on most SQL servers (i.e., equivalent to Informix TEXT with a maximum length specified). We need to decide whether it is better to store our string information as either CHAR() or VARCHAR() under Informix. Thanks in advance. Mitch