In general, I think OHMs will hold the advantage over Maggies in regards to macrodynamics. So if the music benefits from having really good slam and meat on the bones, especially at higher volumes, the OHMs win. That's what led me to replace my long time Magnepans with my current OHMs.
Other than that, I really think which sounds better will depend largely on the overall setup including accounting for room acoustics. The two are both very transparent, yet radically different in design and will sound different accordingly, but either when tuned in optimally can perform exceptionally well in most other regards. Which sounds better in any particular setup will likely depend on so many other factors, that it is a wash in regards to which is inherently "better".
The only thing else I would say is that I am personally a big fan of the Walsh driver approach due to its ability to make recordings sound more "real" or "lifelike". ALong with that, is perhaps the converse that recordings sound less like what most people are used to hearing with recordings perhaps with the OHMS? In that case, Maggies and even other more conventional box design speakers might have the advantage, with the Maggies occupying perhaps more of a middle ground in general (but not always) between the typical sound of a recording and sounding more "live" or lifelike"
