Last year I had to take a quite similar decision. I went for a white dial chrono 25860st and a black dial 15300st. For me itīs an almost perfect combination.
So I would go for the 26331 silver/white dial as it is also quite dressy and fits with any outfit in the office. Itīs also more interesting than the clean 15400 which I would try replace by a 15400st blue/black dial on short term, and by a 15202st in the long run. The latter would be the ideal combination for me.