The Redhawk and Super Redhawk can shoot some ammunition that the Super Blackhawk cannot because the DA guns have longer cylinders which allow very heavy bullets (>300 gr) to be seated further out thus allowing for more powder capacity and thus higher velocity without increasing pressure. This is only really an issue, however, with certain boutique loadings like Garrett's 330 gr Hammerhead or handloads using particularly heavy bullets.
Up to 300 gr, it really doesn't matter and I, personally, don't really have much need to shoot bullets that heavy in my .44 Magnums (I'm perfectly content with 240-260 gr bullets myself). Honestly, if you want or need more power than a normal .44 Magnum can provide, it seems to me that you should consider simply buying a revolver in .454 Casull or .445 Super Mag rather than trying to run the .44 Magnum at the ragged edge. I, personally, feel no need for anything more than a good ~250 gr Keith bullet at 1200-1300 fps as that will shoot clean through anything I have any business shooting at with a revolver.
Up to 300 gr, it really doesn't matter and I, personally, don't really have much need to shoot bullets that heavy in my .44 Magnums (I'm perfectly content with 240-260 gr bullets myself). Honestly, if you want or need more power than a normal .44 Magnum can provide, it seems to me that you should consider simply buying a revolver in .454 Casull or .445 Super Mag rather than trying to run the .44 Magnum at the ragged edge. I, personally, feel no need for anything more than a good ~250 gr Keith bullet at 1200-1300 fps as that will shoot clean through anything I have any business shooting at with a revolver.