Throttle body is the easiest to install.
I went ahead and did that yesterday and was very easy. Throttle response is improved and I get through mid-rpms really quick.
I'd say like most everyone else between 1800-4000 rpms the throttle-body shows improvement in the car.
If you don't have to pay anyone to do it or can do it yourself or with friends, then do the exhaust as it will give you some great sound and performance, otherwise I'd go after the low hanging fruit as that's a slam dunk install and has good gains as well.