I quite like the A-10. And in some edge cases (IE, vs. ISIS), it is unequalled and unlikely to be equalled any time soon.
But having the capacity to deliver lots of bombs counts for very little if the plane cannot get to the battlefield in one piece. Or, for that matter, if it cannot get back out.
The kind of long-term loitering on the battlefield earlier comments seem to speak of is now, I believe, relegated to drones. Which can be deployed in larger numbers, can stay in the air longer and are, most importantly, much more disposable than an expensive fighter and its irreplaceable pilot.
As to the F-35 vs. A-10 trial, I think simply deploying AA in realistic numbers and varieties would well and truly bake the good old Warthog's goose. I can see no real need to artificially skew things, looking at things from the F-35's proponents' PoV.