MBR magazine will tell you that you absolutely have to have a 15 or 20 mm through axle as otherwise your front wheel will fall out and you’ll die. A bit like when they said v-brakes were unsafe when one bike in a test still had them or that square taper cranks will round the tapers and fall off.
I’m just building a new Cove Stiffee frame and I’m using some QR Fox Float 130 forks from a few years ago and I’m sure they’ll be up to the job, I remember the factory GT riders riding the world 4-cross on Rockshox Judy 100s with QR’s and they never had issues.
I noticed the difference in stiffness going from 32mm QR forks to 36mm 20mm forks, but I think alot of that is down to the larger stanctions and the stiffness of the frame (I’d gone from an old Intense Tracer to a 6″ travel Rocky Mountain Slayer). I’m quite happy with the QR forks for my hardtail, the 15 or 20 mm forks just look a bit tricker, but I’m not sure the performance benefit outways the cost.