For the serious pros who pay models, pay for travel shoots or get paid by Fortune 500 firms for unmatched content, the added differential quality between modern MF (Fuji GFX) and FF (Including the A1) MF is inherently better.
SONY/NIKON/CANON fanboys notwithstanding, there is in addition to a 100 MP sensor a ≈ 30% resolution gain due to the simple increase in focal length/entrance aperture for say, standard lenses at similar f/stops (50mm to 80mm). Example:
Sony Planar T* FE 50mm f/1.4 ZA (λ[.00005] ÷ D[29.4mm] [@ f/1.7] = 1.7x10-6rad
Fuji GFX 80 f/1.7 (λ[.00005] ÷ D[47.1mm] [@ f/1.7] here bokeh is identical or better = 1.06x10-6rad
It's λ/D = Angular Resolution (rad) where "D" is the entrance aperture.
The above example resolution difference is 37% better (smaller) with standard lens and this advantage carries through to all commonly used lenses regardless of apochromatic corrections.
Of course, SONY makes money selling sensors, the real issue is why serious pros who have their own cash on the line and who seek to offer demanding clients unmatched quality, have reached and continue to reach for leading digital MF products. Their clients can see the difference.
This isn't just a sensor or megapixel capacity advantage – the MF resolution/noise advantage extends to all common lenses. SONY knows it's run up against this performance wall and thus ramped up their A1 hype.
Is the A1 a great camera? Certainly. The 8K video alone makes it desirable along with a crucial ergonomically class leading viewfinder. However, with stills as the final product, on expensive photo shoots with expensive models and demanding Fortune 500 clients, the MF tools continue to predominate.
BTW Fuji has other unmatched systemic secret weapons...but we'll save that one for later.