Well, yeah, it's not a good idea to mix them because it's like taking a much higher dose of either. Technically etizolam is a thienotriazolodiazepine (an analog of typical benzos). If you're still having trouble with panic attacks despite taking klonipin, haven't you discussed this with your doctor?
[edit] sorry I just saw you've posted some more. Yeah, don't mix them. Take one or the other but don't risk using both unless you know exactly what you're doing.
I'll leave it for others to chip in on whether one works better than the other for panics, but generally those are questions best directed to your doctor or psychiatrist. Have you tried finding a different doc?