Mellow, if you were asking about which of these to get for self-defense, I'd say get the .45 ACP. I'm not an expert, but I have read the opinions of those who are experts and they mostly agree that .44 ACP is one of the absolutely best self defense calibers out there, while .44 magnum is overkill for most self defense uses.
However, you already *have* one gun in each of these calibers. So what *I'd* probably do if I had a few hundred dollars to spare on something for fun is skip the gun and buy a new rubber river raft. But I am obviously not you, so I'd say have fun deciding and more fun playing with your new toy. ;-)