Both are nice, though I think the 5119 is nicer. My choice would really depend on what I'm looking for in terms of versatility. The 5119, while nice, is a much dressier watch than the 5196 and it can't really be dressed-down. The 5119 is also a very nice interpretation of one of the most classic and identifiable of the Calatravas; that is, the 3919. I do feel that the 3919 was just too small, and at 35mm, the 5119 is better suited to the modern wrist. The display back is a nice addition, too.
The 5196 is more versatile and can be dressed up or down more easily. I don't think the case dimensions of the 5196 retain the harmony of its ancestors such as the ref. 3796 or the ref. 96. No display back with the 5196, of course, which is unfortunate.
Bottom line for me, if your looking for a true dress watch, definitely opt for the 5119.