what is the most favourable/preferred type ?

That depends completely on the breed its used on
Archer

Depends on the breed and the individual dog (and the handler)

I have one setter shown on a light chain, another on a heavy chain, andother on a thick rope slip lead!

within my aussies one is on a chain, another on a leather, I always find which lead suits the dog best, and like one I like, saying that I hate the thick rope lead but the dog goes well on it!

If I could I would show all dogs on a long fine chain with a leather handle on the end!