Difference between Auf Wiedersehen and So Long

AUF WIEDERSEHEN vs SO LONG: NOUN

Ciao, Good bye, Good by, Bye bye, Good day, Bye, So long, Goodby, Cheerio, Goodbye, Adieu, Adios, Sayonara, Au revoir, Arrivederci

Bon voyage, Bitte, Wunderbar, Auf, Meine, Danke, Farewell, Bye, Goodby, Goodbye, Adieu, Adios, Sayonara, Au revoir, Arrivederci

Andrew Dickinson, Third Country Mandatory Rules In the Law Applicable to Contractual Obligations: So Long, Farewell, Auf Wiedersehen, Adieu?
Normally Monsieur Candie, I would say, auf wiedersehen.
Auf Wiedersehen Blackpool, wir fahren dorthin, wo es auf Sonnenschein eine Garantie gibt.
Auf Wiedersehen, Auf Wiedersehen und Auf Wiedersehen ist Wachstum.

It takes so long because I have so many objects.
No one deserves to feel so inadequate for so long.
Jonathan conned so many people for so long.
Morgan said that some people must be a long way from God because their prayers are so long.
As can be expected with books written so long ago, the originals have long since vanished.
How Long Should A Loan Modification Take And Why So Long?
United States so long as the charges are pending or to leave Pakistan so long as the red notice is pending.
So long as a long way early days crude techniques.
So long as roads were tarred blue and straight; not hedged; and empty and dry, so long I was rich.
So long as the letter is regarded as sacred, just so long can anything, even pure materialism, be proved from that volume.