Well, you might not like this, but it depends. What am I basing my decision off of? Is it overall effect presentation, the performer who teaches the effect, etc.
If we were going based off of just the trick itself, I would say Distortion, it is a beautiful effect and amazingly simple. Panic is a crowd pleaser, and extremely visual, but it all depends on your personal preference. I would check out some reviews on the effects, check out
this thread for some reviews on both products.
Take care,
TDA