Go read the whole thing for yourself, but I've never found the rationale for STOVL very convincing. The Marines want to be able to operate from remote bases close to the battle, but a first-class Navy ought to be able to seize and build landing strips, position aircraft carriers, refuel in mid-air, etc., so as to obviate the need for STOVL. Our allies, the British and the Italians specifically, operate small carriers that rely on STOVL aircraft. So it makes a lot of sense as an export. But the added cost in R&D is substantial, and it has long since become a serious drag on an already expensive program.
If the Marines ever get into a situation where they are dependent on STOVL for close air support, we will have already lost the battle.
Building an airfield takes a long time. That won't happen in the early hours of an attack. Capturing an enemy airfield and using it to stage F-35s closer to the front or using a section of highway is more likely than the notion we'd land in a rock-filled field. Heck, we might face an enemy with anti-ship missiles that prevent us from getting big carriers too close initially. So I think the F-35B's ability to operate from less than pristine facilities is a good capability to have.
But mostly, I like the F-35B for the capability it gives us to equip our hidden aircraft carrier reserve fleet:
These [small carriers equipped with F-35s] will outclass anybody else's actual fleet carriers. And we don't even really count them as carriers. Yet they'd do perfectly fine as carriers in a pinch and would be able to carry out various escort and ASW tasks quite well and free up the big decks for offensive action. They will be able to lead expeditionary strike groups.
If we don't need to lift a Marine Expeditionary Force with one wave, we'll have these vessels available even though they don't rate a mention as a part of our carrier fleet, yet are comparable to those small carriers of our allies and potential foes. And the F-35B is recognized even in this critiwue as appropriate for those small carriers.
We have a reserve carrier fleet hiding in plain sight needing only an aircraft to be able to strike hard against enemy sea and land targets and control the air.
Build those F-35Bs.