It depends what JD and what MBA.
A University of Phoenix MBA isn't worth the paper its printed on
But even a Cooley JD opens the door to the bar
A Harvard MBA and a Havard JD have different potential upsides and downsides. The Harvard JD will likely have moderately high, but steady earnings. The Harvard MBA may start lower, but have significantly greater upside.
In general, the MBA is probably more versatile.