Considering the best one I have at the moment is one from POTV that came included with something, And so long as I can work the grinder, what comes out seems to be working for me.
The large BCG is larger diameter than the OMD. More leverage. The grippy addition for OMD probably does help, for same reason. I had the BCG first, bought it specifically because I was having a hand issue.
The OMD is a wonder, being SS and sleek with the bearing. But if I were buying my first high quality one, it would be the BCG large, aluminum, with coarse grind plate. (Alminum is not a deal breaker for me.) For times I want a finer grind, I grind upside down for a couple of turns first. OMD does not have a coarse option. Grinding coarse is easier on the hands, and quicker than using a plate with smaller holes.
The OMD weighs a full pound, as I recall.
The lid on the BCG lifts off (use a clamshell action) easier, a reasonable magnet, though you can also order OMD with no lid magnet.
If you can find a BCG second in a color scheme you like (large/coarse) it would be a good score. Usually, you can't even find any "defect" on them.