In guns of the strength class appropriate to the .44Spl, like mid-frame single actions, it has the definite edge. In Colt SAA's, replicas and mid-frame Rugers you are fully capable of pushing the Keith 250gr SWC to 1200fps in the .44Spl and the cartridge is much more efficient. In similar guns, the .45Colt must be kept to 1000-1100fps at the absolute most.
In large frame guns like Ruger Blackhawks, you're really only comparing the .45Colt to the .44Mag. Here is where the .45 starts coming into its own, where you can start using some of its cavernous case capacity. It can be loaded near .44Mag velocities with similar bullet weights.
Where the .45 really shines is in strong rifles like the modern 1892 replica, the Ruger Redhawk and in custom five-shot revolvers. In 1892 rifles, 260's can be pushed over 2000fps at 40-45,000psi. In the Redhawk, there is plenty of 45-50,000psi data in circulation. In custom five-shooters, you're up to 55,000psi and rivalling the .454.