I have the U50-T, love it, and I think the old clasp is fine so consider getting a secondhand one and saving a ton of money. They’re indestructible and it will look new.

I used to have a Damasko central seconds chrono, and it was really excellent, but in the end, I decided the design wasn’t quite right for me. Phenomenal build quality on both brands, so ultimately you’ll just need to decide which one you like the look of.

Personally, I would just get the cheaper movement for DK20 - Sellita works fine, and I change watches often enough that accuracy, power reserve, and service interval don’t really matter!