If road aero helmet selection is anything like TT helmet selection, you will find that there is no single “best” helmet for everyone. Plenty of testing with TT helmets shows that some helmets work better for some riders vs others.
I expect road aero helmets will be similar, where there is not a “best” for everyone either. Overall body position, head angle, relative head position to torso and such will all play a part. Chances are likely good that any aero helmet will be faster than a regular vented one though, but I bet there is an exception hiding in there too. 