Both are very good quality shocks. The RE Monotubes (which have a lifetime warranty) ride well on the street, are what I run, and they work very well offroad. The OME shocks have a great reputation for their street ride, I'm not so sure if they are as good as the REs are offroad though.
So if it's primarily for the street, the OME might give you a little better ride but not significantly. I'm happy with my RE Monotubes both onroad and offroad but I won't vote on this because I don't really know how important street vs. offroad use is to you.
I know nothing about Dune Grapplers.