Does Exim or Postfix, which run better in Ipv6 ?

[<kmlhk79-ipv6@yahoo.com.hk>]

Dear All:

In Debian, there are 2 email commonly use email
packages Exim and Postfix.

Which one will work better in Ipv6 ?

I read some old news that Exim had bugs on Ipv6.

"Exim: Two buffer overflows"

Does it fixed ? 

Since Exim is the default Email agent for Debian, Will
it work better on Ipv6 ?

K. M. Lau