Not Tiffany, but I have an A. Link .51 carat dbty style necklace. I had a Tiffany dbty in .41 (but returned it) and feel like Tiffany's .41 is almost the same size as A. Link's .51 carat. This is because Tiffany's dbty diamonds are more shallow so the table of the diamond is quite large, giving the illusion it is much bigger than it really is. My A. Link diamond, on the other hand, is very "deep" so the diamond sticks out a lot from the bezel.
In any case, I really prefer A. Link's chain more - it's thicker, much more substantial and doesn't tangle as easily as my Tiffany necklaces!! Here it is with my Tiffany three diamond pendant in platinum (which has turned quite greyish):