Going to buy a new spare 2k2 Jetta ECU, need advice

I want to order a spare ECU so if I ever need to take the car into the dealer, I can just swap the ecus real quick from the chipped one and not chipped. But does anyone know what I need to find out before getting the ecu and about how much? I know some car manufactures have different ecus for different models of cars or 1/4 of the year cars. I just want to make sure I get the correct one for my car.
Also, what is the best performance chip out that will give me the most power with the best reliability. I plan on making the car fast as hell as well. I have heard alot about APR, but not sure about the others. APR is more expensive but you pay for the best quality I am sure.
Thanks guys!