chip or stand alone

A tuner (PMS, TwEECer, EEC Tuner, EPEC, etc..) will allow changes where as a chip is burnt for the combo that you have that day, re-burns or dyno time can get expensive as you make changes.

However if you do not have the knowledge of how things work a chip is the best choice.

How modified is your car? Why do you think you need either?