lordy.
Senzel was a 60FV and Riley was a 55FV. i feel this gap has grown, as i'd keep Senzel the same and move Riley down a bit based on his issues.
Senzel has a better minor league track record.
Riley came up and K'd 36.4% of the time with a 5.4% BB rate. his issue were/are absolutely glaring.
Senzel came up and and K'd 24.4% of the time. that difference is enormous. 7.2% BB rate...also a good bit better, especially compared with the K-rate.
Senzel is a better defender. i'm not sure that's debatable. perhaps it was a knock on him when drafted, but much like Riley, it's not anymore, but he's still a better defender who will also help more on the base paths.
Riley's wRC+ is heavily thrown off by his very unsustainable hot start. once pitchers found his weak spots he was getting eaten alive pretty much every single AB. Senzel didn't have nearly the same degree of problems.
IMO Riley's issue(s) is/are glaring and no one knows if it's something he can really fix. he's completely guessing up at the plate and pitchers know it. Senzel doesn't have the same kind of issue. Senzel is a better, more valuable piece.
so all of that is context you're leaving out.