This is between Beyonce and Jennifer. Beyonce's voice is much more dexterous than Jennifer's, but nowhere near as powerful. I think they probably have a similar range, although Jennifer is more comfortable in the contralto range whereas Beyonce is probably more of a pure soprano.
Alicia strains too much. Jennifer is LOUD and doesn't have good control. Of course, Beyonce has a flaw or two, but she slays in so many different areas.
I don't think Beyonce's voice is as difficult to control as Jennifer's because it's a bit thinner. She's dealing with a machine gun while Jennifer's got a bazooka. A poll like this is really just going to come down to personal preference.
But one thing's for certain: both of them can sing Alicia Keys into the ground.