"in favor of" usually means the second thing is better than/preferred to/replacing the first. It is kind of confusing here.

Sometimes difficulty in simplifying a sentence means that it is trying to say to much or working too hard to get there.
What about changing this to be more direct than the original man page wording, like so:

This example shows how to use
.Xr dma 8
as a replacement for
.Xr sendmail 8 :

That could be even simpler:

Using
.Xr dma 8
to replace
.Xr sendmail 8 :