Time doesn't change pressure but it does change bullet selection. In the current Hodgdon manual, we see 330's at 1350fps and 355's at 1250fps. They beat the .45 by 100fps at similar bullet weights. I've verified these velocities in my own guns.

The difference in pressure is irrelevant. However, looking at starting loads for the .44 and max loads for the .45, what we see is that the .44 produces the same velocity at the same pressure. That extra pressure is not for nothing and goes into that extra 100fps.

While we're quoting Seyfried, let's not forget that he used 350-360gr bullets on his Cape buffalo.

The overall point being that the .45 is not better with heavy bullets and the two are all but interchangeable. The .45 'may' be a tiny bit bigger (depending on meplat size) and the .44 may be a little bit faster. The difference is a wash.