The mobo that they wont to give you is a down grade.
but only in one category that matters if you use it for this reason

Yours had a dvi port on it and that's useful as a HTPC setup.. 

Both mobos  are basically the same chip set ...Nvidia renamed them
And all that was  is just a pure marketing move to save money at least
that's what I read. but both boards should perform just the same
with the existing hardware that you have. And what you use it for.

As for which one would I chose would be the ASUS M3N78-EMH 
Why.... gives your dvi back pulse a hdmi port and and is a newer chipset
that  supports dx10 Over your dx9 board. hope this helps i glanced over
all three of these mobos im sure I could find more points but from what
I seen I only talked about what would matter.