Question about Dell UltraSharp U3818DW

I bought the following product on sale a few weeks ago for CHF 599: BenQ EX3501R (35", 3440 x 1440 Pixels) However, I am not happy at all with the picture of the display (grey/black as well as colour tones and contrast). You can see vertical lines on the side edges. I can't judge it for gaming, but it's terrible for office work (IDEs). My question is whether the current 500 franc price difference is worth it if I were to buy this Dell monitor instead of BenQ. Does anyone have more accurate observations for homogeneity and depth of colours, especially grey/black and image contrast? Best thanks