Serious study. I’m really doubtful such a thing has been done, and even if it had, one would need to look at the funding of it (e.g. marketing body for organic wines or similar for the suppliers of non-organic treatments).
Running a simple comparison is almost impossible, as you’d ideally need a chequerboard arrangement of a vineyard to apply organic / non-organic treatments to negate the effect of terroir, but if spraying, then cross-contamination is a given.
Running before / after trials runs up against vintage variation
Then there are variables it’s difficult to precisely replicate from picking through to finished wine
Then the clincher - the old chestnut of how do you measure quality. Blind taste tests are an option, but our palates differ, so the result is merely representing what those judges thought, not a meaningful measure of quality.
So I’d be surprised (and very doubtful) if there were any scientific studies that would survive peer group review.
What could be tested, I suspect quite easily, is that assertion of the level of roundup compared to human perception levels for it.
Now to the anecdotal experience. I’m sure there are many wines grown organically that you love, but the almost certain reality is, that it will not mention organic on the front label, and almost as certainly on the back (though those paying for certification may have the logo to show this).
I’m also pretty sure that the ones you tried with ‘organic’ proudly displayed on the front label have been very disappointing. The sad reality is that there is a market for the branding ‘organic’, where the quality comes behind preserving that brand, plus getting enough volume to make the product profitable. Interest / quality are no more the focus than other commodity / heavily branded products. These wines are really a variant on the Gallo / 2 buck chuck, just aimed at a specific but reasonably numerous subset of those that see wine the same as other commodities.
Conversely those that quietly follow organic / BD (and let’s extend this to Lutte Raisonee), are people who do so simply because they are looking for ways to improve their wines. It may be successful or otherwise, but their willingness to try what they can to improve them, seems likely to extend to their whole approach, and that suggests someone putting quality much higher in their priorities.
Regards
Ian