[exim] Is Exim easier to customize than Postfix?

Hi all,

I really don't want start a Byzantine discuss about Exim vs Postfix, just
want some criteria and advice from the wise and experimented people of this
list ;)

One can read everywhere that Exim is more flexible than Postfix. I'm
interpreting those comments as: "out the box Exim can be more customized as
well as flexible than Postfix just changing configuration variables".

But in case that I need do things that are not possible do it with the out
the box configuration variables (I'm thinking in the integration of custom
logic very deep inside the MTA mechanism) is still Exim a better option
than Postfix for that?

I'm excluding as an option the source code modification of any of them, the
integration and management of the MTA process will always have to be using
plugins or well documented interfaces between the components of the MTA.

Thanks in advance.
Frank