Assuming your car is a '96-'99, the GReddy kit will essentially bolt up and run no problems. The RevHard kit can be bolted on as well but to get it running smoothly you need to add a few more things. However it also has the potential to make more power and has less redundant parts if you decide to start upgrading things.

Which one you choose has to do with how much tuning you want to do and how much upgrading you would like to do of the kit in the future.