What a great discussion. I've shot with both zooms and primes over years. I started with primes with 35mm, 6x7 and 4x5, then moved to HQ zooms with the digital revolution. I loved the zooms for the travel photography I was doing. I didn't always have the opportunity to slow down and switch primes.
But now I'm back to primes for my serious work and have a zoom for snaps. The reasons:
- for the price of a zoom of high enough quality and brightness, I could purchase a few primes;
- three primes weigh less than the equivalent zoom;
- zooms inherently have more distortion than primes (especially wide zooms which may be moot here as you are talking about cropping the middle out), distortion that is often more difficult to correct in post; and
- Bottom Line for me: zooms made me compositionally lazy. What I thought was the "best" composition with a zoom was too often the result of convenience rather than working for the "perfect" composition - often a more dynamic composition - that matched what my mind was seeing. In an uncanny way, primes make me more "explorative" than do zooms.
So, while I have gone off on a tangent, I think it is important to look at the whole context of primes vs. zooms if one is basing this discussion on which to buy. Until one has really explored the advantages of each weighed against the type of photography one does, to limit the discussion to only one aspect of quality is useless. In the end, the pixel-level quality - which what the OP first asked about - is irrelevant if you aren't using gear that works for you in the way that you
see and work.