Great topic, in my opinion. I've wondered what the allure of First vs Business was, especially as flat beds in Business are becoming more commonly available. I have been in Intl F only a couple of times, most recently LX on the A332, which is much nicer than C on the LX A332 but the C seat on other airlines is usually nicer than LX's A332, and to me, comfort is mostly about the seat and space.
Given the price and points differential, to me, it's an easy choice to move from Coach to Business when using points. You generally need ~50% more points to move up. You get much more space, comfort, and service.
To go to First is often at least 50% but sometimes even more expensive.
I've always been content getting Business, am I missing out on a whole new experience? Is it worth it?
I've usually looked at the decision as the difference between 3 trips in C vs 2 trips in F. C has been good enough, even angled-lie-flat. If I'd been flying full-flat or F much more often, then I might not accept a angled-lie-flat as easily. Same with aircraft, if I had been used to avoiding middle seats (eg. A330/340/380, B767 in C, or herringbone, or anyone in F) then I might look down on a more cramped configuration (eg. the middle seat in C on a 747/777 in the 2-3-2) and set my sights higher.
Maybe a topic for one of your future podcasts?