They haven’t stopped the inflight chef, IME. He was inflight a few weeks back in F on the A330 service to GVA & the food, beverage & service were (as usual) spot on. The chef makes a massive difference in customising & presenting food beautifully.
I think it depends on the route then, DEL and BOM did not have the chef. In my experience the food was of an identical standard to when there was a chef, the only difference was that my order was taken by a flight attendant (maybe the purser) as opposed to a chef.
Reverting to the OP's question, F is better than J, if you want better then pay for it (even if in miles) if you're happy with J then go for that, although avoid J in the 330/340/777s.
In fact, considering you're using miles I can't think of a better use of miles (your MR points) than Etihad F on the 380; so I don't know what you're saving them for... and I don't think there is much point in doing that.