Photography

I'm just an amateur, so maybe the answer will be different for a professional, but I doubt there's much reason to upgrade a single version as long as your gear is supported by the older version. Maybe wait 2-3 main releases. Ultimately, the buy-once nature is the main reason I initially started using DxO instead of Lightroom. If I'm going to buy a new version every year I might as well just get an Adobe subscription.

DxO does a small handful of things genuinely better, but I think most people will be better-off with Lightroom most of the time. It's easier for beginners to find good tutorials, the updates happen quietly in the background instead of nagging you every week, and the tools for stacking, masking, and local adjustments are just SO MUCH better. Plus if you use local storage you get Photoshop basically for free.

DxO has a UI that's easier for a native Windows user to understand, the AI noise reduction tools are a bit more granular and don't make a second file, and it's got a bit more adjustment range for white balance if you shoot in really weird light; I once shot a band lit under predominantly blue lights and made it look natural. For most users that's a pretty short list of benefits, which leaves "you don't have to buy it every year" as one of the biggest selling points.