au dela v. par dela

[alan gould]

is there a difference?  

[Chantal Savignat]

very very small and very hard to explain.

au-delà is more used.

par-delà is more literary.

I would say that "au-delà" is just to indicate "on the other side" and "par-delà"  is used for the same meaning but with an idea of obstacle. 

[alan gould]

i'll just use au-dela all the time.  Tx