So, path-dependencies (e.g. "What card is loaded in to my PayPal account?") and fiddly spend bonuses (e.g. my country club logs as a gym/health club, so I get double points on the Hyatt card, and that's $12-18k/yr in dues plus F&B) aside, food and travel goes to CSR. "Everything else" goes to (generally) Hyatt, American Airlines, or Amtrak, but I treat the three as "mostly undifferentiated" (though Hyatt probably has the edge among the three) since the status-earning/bonus-earning propositions are all pretty similar. As long as I have my company, nothing personal really goes to Delta (even Delta travel - again, it's not the points earning, it's the crap TI coverage Amex offers) unless I have a big tax bill I can't put elsewhere, save for a small mix of items that I'm reclaiming credits on (e.g. Resy and rideshare). It just really is a lousy card.

If the Reserve went to 1.5x miles across the board, there's a good chance I'd move a decent amount of spend over.

One observation, and I think this is a fiddly gap: There are doubtlessly folks in a position where they have both cards (business and personal) and spending to $75k on both really gets them "nowhere special" (and if anything, the personal card gets deprecated due to how the business card works, with the 1.5x miles over there). I wonder if there is anything that could be done to address this? Really, just going to 1.5x miles after $X spend on the personal card would fix most of that; that's the "real" difference.

And worth noting - getting stuffed into running my family business (and so getting to direct all of the CC spend) is the only thing that actually kept me with DL on the CC front. Absent that, I was just going to sock drawer the card and plan on only flying Delta a few times a year (cross-crediting to Virgin Atlantic) while shifting my business to AA/AS/BA. Mind you, BA's stupidity would've also forced a plan shift, but that's just another quirk of DL's incentives.