Doubling down on that point a bit more - I think that, assuming the study is high quality, one that looks at all the popular artificial sweeteners together is

Doubling down on that point a bit more - I think that, assuming the study is high quality, one that looks at all the popular artificial sweeteners together is probably more valuable from a "practical application" perspective, because it allows you to make more of an apples-to-apples comparison among the individual sweeteners. If all you've got is bunch of isolated studies that only look at one of them at a time, you'll always have some room for doubt about whether a difference in outcome reflects the sweetener being tested, or some difference in the experimental protocol.