The choice really is yours and yours alone. Though I personally never used Gibbs I have seen others use it. It looks like a good software, but so is Mastercam. You may want to concider that more use Mastercam than any other software. I too use BCC V17-21 and now Training on MC V8 and V9.
If you already used Gibbs stay with it unless your looking for more. Then go with MC.
The choice is yours really. Go with what you think will be best for what you make.