Interesting, I have always used pencil jets, couldn't see no reason why a fan jet would make a difference.
A few weeks back was working and snapped me carbon goose neck, rang me mate who had a few spares and bought one off him, it came all set up with brush head so just connect hose up and off I went.
As it was fitted with fan jets, I was like wtf this will be garbage ............ I am now a fan jet fan !!!!!
It may just be me but it seems to clean debris and bird muck off better/easier so to say.