Tune-Bot Gig givs you the important tools from the original Tune-Bot, but cheaper.
This means that you get the same reading algorithm and such - just cheaper and with a more simple and user friendly interface.
What you do not get in the Tune-Bot Gig is internal memory and the 3 tuning modes.
On the other hand, the Gig model is easy to use. There is an on/off button, a button for switching between the two modes "Absolute" and "Difference".
Absolute mode is used to read the frequency at each lug (lug pitch) or for the entire drum (fundamental pitch).
Difference mode is used when tuning the lugs according to each other. It is a bit like you know it from a guitar tuner. You put one lug as the "master" and the other lugs are read according to this "master" (+/-).
You get a cheap and efficient tuning solution with the Tube-Bot Gig when you need to make your drums sound awesome.