I'd go with the 1275, just for the extra power. It really depends on what you wanna do with it.
Personally, I want a supercharged 1275.
Depending on the condition of the 997 and your plans for the car, you may save money by using what you have. If your parts are worn or broken, they'll have to be replaced, but I'd think that would be cheaper than getting a brand new 1275.