IMHO, Keep the Colt. It will be worth more down the road and is a better gun now.
If you get rid of it, you will always regret the decision.
If you keep it, you can always buy another gun to add to the collection.
If it was a good deal, the other guy would not be eager to make the deal. After all, he knows what he has now and wants your gun instead of the one he has.
I had a Colt Officer's model in .45acp that I let an attorney in my office talk me out of back in 1997. To this day I regret letting that Colt leave my collection. I have offered the guy twice what he paid for it so I could get it back.
Keep the Colt. Five years from now, you can thank me for the advice.