A -vs- CNAME

[William Webb]

I had  an ISP request that a  batch of CNAME's that pointed to one 
address all be changed to A records pointing to the same IP 
address.  He  said this would allow his server software to operate  
"more efficiently."   I  realize that the reverse, changing from a 
CNAME to an A record can actually cause problems with some  
operations like sendmail,   but I have not heard that an   A  record   
could result in more "efficient" server operation than a CNAME.  
Does anyone have an explanation for how that could be possible?   
Are we talking about 1/25th of a second less DNS lookup time?