All in all, I really enjoyed my F experience with Asiana over the J experience.
Here are some differences in no particular order, but I say if you have the miles, do it!
- In LAX - access to *A first class lounge - quiet and a la carte dining
- In ICN - personal escort from check-in counter to lounge (note that the lounge is not a huge upgrade from J - big difference is there is no crowd)
- In ICN - personal escort from F lounge to boarding gate
- fully enclosed suites
- better amenity kits (Ferragamo)
- Pyjamas
- more personalised in-flight service (had about 4-5 staff for 3 passengers!)
- F has caviar
- F has upgraded champagne (I believe Baron de Rothschild) and wine
Note that I do not know if you get F lounge access on your outbound flight.