For what it's worth, I think F is highly overrated on CX. You get a bigger seat, plus some other things that many would probably not pay for if they were offered ala carte.

For example:

PJ's (nice because they appear "free", but would you buy them in a store?)
Krug and cavier and ultra-premium booze (nice because they appear "free", but would you pay extra just for that? And how much of that do you really consume in a flight?)
Dine on Demand (is that really such a big deal?)
Mattress and Duvet (Yes, this is nice.)
Access to The Wing
Service not much different (Better of course, because two FA for 6 PAX. But they still mostly hide in the galley waiting for you to push the call button.)

If you look at this by mileage burn, there is a 50% premium for first class. I do the math something like this: A J ticket could cost perhaps $6K, or 145,000 Asiamiles, which puts the value of the miles at around $0.04 each.

A "F" ticket is 220,000 miles... or a 75,000 premium. At $0.04 per mile, that values the upgrade at $3000.00. Given that the J product is pretty good... is the list above worth $3K to move to F?

On the other hand, if you are using AA or AL miles, the upgrade is SUBSTANTIALLY less, and probably worth it. 140K miles for F, or something like that, vs. 100K for J. And the miles cost less. And it goes without saying that if you have oodles of miles to burn, then for sure use them up on F!

I have done F a number of times simply because they were the only seats available at the time of booking. I have tried to "downgrade" to J prior to the flight because for the same miles I can fly 3 roundtrips in J, or 2 in F. (Have not been able to downgrade because no guarantee of a return flight in J, and then I'm paying for one-way awards in both J and F, which are something like 80K and 130K, or 210,000 miles total. For the extra 10K, I'll definitely choose F roundtrip! :-D)