I personally have used Old Bay exclusively up until a few years ago. That's when I discovered J.O. seasoning.
J.O. is spicier... better suited for steamed crabs, IMHO.
I still like Old Bay... use it for spiced shrimp.
But now, when it comes to steamed crabs, I use J.O. exclusively.
And, the vast majority of Maryland crabhouses use J.O. to spice up their crabs. That should tell you something right there!