well with a chip, its a one time deal. usually you do a dyno and they match all your mods to your computer and hopefully get it perfectly. if you change anything then you have to get it reburned. the computer tuner lets you change all the aspects that the chip does but you get to do it over and over and experiment with different things. as a person that just got ahold of his twEECer about a week ago, id say in a month or maybe a few months ill be able to change things on here that i dont even know about right now but i have done something things with the tuner to help my car already. if you dont like reading and experimenting with numbers then just do the chip and get it over with
well the computer in the car has the acronym of EEC (cant think offhand what it stands for). the twEECer (pronouced tweeker as in tweeking your car/computer/etc) was just a cool name they thought of.