I'm not sure if this is completely helpful since I own the MX985 and MX375 and not the earhook variants, but here's my take on the differences:
In terms of sound, the MX985 is much full-bodied and rich with deeper bass and more extended treble. The MX375 doesn't have the same amount of detail (in terms of articulation or texture), but does seem a bit more airy with a larger soundstage.
Ergonomically, the MX375 housing seems to fit my ear better, while the MX985's housing is a bit on the thick side. I'm thinking the earhook of the OMX980 might help a bit there, but I would recommend trying them out first if possible.
The build would certainly be better on the OMX980 as opposed to MX375/OMX185, but that goes without saying.