The manufacturer contrast ratings are almost irrelevant, many times the numbers are exaggerated using some specific measurements that are not the best way to measure contrast ratio.
What you need to do is look at the reviews of the monitors and see the actual tested and viewed quality.
For overall quality in a series, I like the Dell Ultrasharp models, in a 24" screen 4k is a bit much, I would stick to 1080 or 1440, depending on how much data you want to cram on the screen vs the size of the text and images you can see comfortably.
I think you should go for the FHD resolution monitor with contrast ratio of 1:3000. Since, you need the display for reading and graphs it should be good choice. 4k Monitor are mainly for gaming at higher resolution. So, full FHD would be good option for you.
My suggest go for the 27inch monitor if you have the budget. It will help you in reading with zoom in option and reducing the eye strain...