The DBTY is in Platinum while the Diamant Legers is set in WG. Personally I feel like PT is darker and more grey-ish than WG which really shines brightly. However, I much prefer PT over WG since WG is rhodium plated, which can wear off over time. I have a RG and a PT DBTY and the PT one looks definitely much "cleaner". My RG is in .17 ct which is has a thicker bezel than the PT .20 one I have. The RG DBTY looks larger due its thicker bezel. I also have a Cartier d'Amour RG bracelet in 0.09ct. I feel like the diamonds in the DBTYs are much sparklier than the Cartier d'Amour, however the Cartier one has a thicker (more substantial) chain, which I prefer in a bracelet. If I were to choose a necklace again, I'd say PT DBTY > RG DBTY > Cartier d'Amour, which is also my rating for the shininess of the diamond.
I find the Cartier d'amour a bit overwhelming with its thicker, sparklier chain and its setting, which I prefer in a bracelet but dislike in a necklace.
However, the PT DBTY one pokes a bit (the diamond is sticking out in the back). Personally I don't mind, but if you have sensitive skin, I'd get either a smaller diamond in PT or the RG in a thicker bezel (DBTY in RG with a diamond size up to 0.17 have a thicker bezel than the ones set in YG or PT. Also DBTY in Silver have a thicker bezel, but not sure about the diamond size there), or the Cartier d'Amour, which has no poking problems at all.