The article Dick mentioned is in the June/July 2000 issue of Handloader (205). The title of it was Turbocharging the 45 Colt. Good reading!

Its always going to be easier to make a wider bullet go faster with a little less pressure all things equal. Can't beat physics...Just depends on how close you want to push the envelope, so with two bullets this close in size, they are going to be very similar, one just does it with less pressure. Personally, I don't care just how hard they can be run, it just isn't necessary. If I need to run a 45/44 that hard, I probably should grab a different gun from the safe in a larger caliber or more case capacity in the same caliber. Go shoot a few more critters with your sixgun and you will see that they nice middle of the road loads work just as well as a fire breather. In the field, I can't tell the difference except in recoil. As alway, the most important thing is to hit what you aim at, so its better to back off the throttle if you have to in order to ensure shot placement.

I stop my 44s about 315 grains and the 45s about the same area in weight and start the 475s at the 385 mark and go up from there. In the lower 48, if you can't kill it with a 260-300 class slug in the 44 or the 45 at 1100-1200 fps, then you probably aren't shooting very well number one and its a fight you shouldn't have started to be honest. The larger 475/500 class of guns are nice but not necessary at all. They are a way to shove a wider bullet with more weight at the same speed mentioned for me for fun but they don't do anything for me that the 44/45 won't do. If I were hunting Africa or something that can eat me, I would rethink it and move to the bigger gun with the bullet weight on my side but my velocity will not likely change. A good hard solid at 1200 fps will do anything I ever want. Hence the reason I don't get in the top end velocity arguments of which is better. To me, it just doesn't play a part in the equation.