OK, I definitely prefer the neck profile and feel of the 2020 JJ Masterbuilt LTD over the 2021 Modern Metroline LTD with the 2020 JJ LTD being flatter and faster feeling. It's not that the 2021 Metroline is bad by any means. It does feel thicker but also does taper to a flatter feel as you move up the neck. The ebony board is also gorgeous. Splitting hairs here really.
As for which sounds better? Tough call. I like both.

The modern is more airy in the high end with some of what some people might call the Ken Smith type honk. But it sure is punchy and big yet capable of sweet and round too. Very, very nice. The JJ is more vintage sounding and not as bright up top and probably better for creating that "pillow" sound. But can for sure get more aggressive and raw too. That open Jazz pickup type feel but not as aggressive as the single coils. It too is very, very nice.
They both feel premium. The raw feel of the Metroline is pretty cool. Sort of reminds me of a Warwick in a way. The Masterbuilt with gloss finish is what you would expect if you have experience with gloss finished Sadowsky's.
I'm keeping both and selling something else.