I've both Sinn and Damasko watches in my collection, I haven't experienced a Sinn 104 however I do have a Damasko DA44 which is the same watch as a 46/47 bar the hour markers instead of Arabics dial.
All Damaskos have the same bezel action as they're designed and built the same way (with the exception of their divers), that is to say that they're incredibly positive with zero slack. Their inserts are laser etched steel with a hardened surface, the 104 has a printed aluminium bezel. The bezel action varies from Sinn to Sinn depending on the model, certainly in my experience anyway, and whilst they're still of a decent standard I prefer Damasko's. The crowns have always felt better on the Damaskos as well, probably due to their self-lubricating nature, though again that's not to say that I've been unhappy with my Sinns.
As for the full lume dial, I've a DA67Si and I'd say that the dial on that provides better luminosity and an easier to read nature at night than my black dialed Damaskos. Neither company, IMO, have lume as good as the best Seikos or even the Tudor I have. I'm pretty sure that you can spec the crystal with AR just on one side, my DA44 has it on both and it shows finger print smudges a bit too much for my liking.
All Damaskos use their proprietary hardened steel, most Sinns are Plain Jane steel. All three of my Damaskos are spotless, the (fully hardened) Sinn 757 I once owned was the same. There's not much in it when comparing regulation, though Damasko just pips it - both have been perfectly acceptable.
Despite what I've typed up above sounding like Damasko tops the charts you won't go wrong with its German stablemate.