Is there a?difference between atrial tachycardia and junctional tachycardia?

Yes.: These are two different rhythms. Atrial tachycardia is an abnormal rhythm originating from either the left or right atrium. Junctional tachycardia is an abnormal rhythm originating from the av node. Neither is more dangerous than the other. The treatments will be different, usually.

Location, location..: Very much so. It hinges on where the problem comes from. I'll skip over pills and move to corrective procedures (ablation). Generally, atrial tachycardia can be eliminated with ~85% efficacy by a good electrophysiologist. Junc. Tachycardia carries a much higher risk of damaging the normal conduction tissues of the heart and significant skill is required to avoid that. A good ep is advised.