Hardcast, before you start reloading for his revolver, check which model it is. One of them isn't meant for hot 45 Colt loads; I think it's the New Vaquero.
Ordinarily, the 45 Colt is quite a bit less powerful than the 44 Magnum. Factory ammo manufacturers have to load it light enough to be safely used even in the old late 1800's made revolvers, which weren't nearly as strong. That's probably where your friend got the idea its not as powerful as the 44. With a strong modern handgun like the Ruger Redhawk or Blackhawk, or the T/C Contender or Encore, and with either hot handloads or +p+ factory ammo, the 45 Colt can compete with the 44 Magnum in terms of velocity and power. As for why people are drawn to them, it all comes back to the idea that "bigger is better." The 357 and 44 Magnums are cool, so the bigger and badder 480 Ruger, 475 Linebaugh, 454 Casull, 460 and 500 S&W Magnums must be cooler, right?
One thing people don't tend to realize when shooting the more powerful revolvers is how harsh the recoil can be. Obviously, everyone has different levels of recoil tolerance, but the fact remains that repeatedly firing a gun that's more than you can handle leads to bad shooting and habits. This is why I will always recommend someone start with a less punishing caliber, or else one that can chamber a less powerful cartridge (357 that can fire a 38 Special, a 44 Magnum that can fire a 44 Special, etc). I definitely see the appeal of the larger cartridges, especially to a newbie, but it's best that they start out small and eventually work their way up.
If your friend would like more information to the capabilities of the cartridges, have him check out the handgunhunt forums:
http://www.handgunhunt.com/forum/ubb...s.php/ubb/cfrm. There are a lot of guys who have a lot more experience than me who would be willing to answer any questions he may have.