Protools, ISTA+ if you're willing to get that set up and take the time to learn it. For convenience I also have a Launch X431 Pro3S+ which is excellent (bidirectional, and does every car on the planet). I find myself using the Launch pretty frequently because it's just easy. I hook up ISTA+ when I have to (fire up laptop, set up ICOM, wire up, etc). Wouldn't mind hearing more about people using Protools for diag. I have the whole setup but really don't use it.