Without knowing what your planned use is, it is hard to give any advice other than the very generic, "If you are going to reload, the .454 is the better choice. If you are going to buy ammo, the .44 is the better choice." Factory .454 ammo is pricey as it does not have the volumes of the .44 Magnum.
I went with the .454 but I load my ammo to a middle ground between factory .45 Colt and full-blown FA .454 Casull. My load is the 300-grain FA bullet at 1200 fps in .454 Casull brass. This is perfect for deer and hogs as it hits hard without unduly beating up the revolver and my body.