U2415, ports compatibility with GPU ports

Most Inspiron and many G-series systems do not allow the selection of the discrete GPU -- the Intel GPU handles most or all of the video outputs, which does indeed change the dynamics of what you can display and at what resolution and refresh rate. 

There are a few G-series systems that do allow the discrete GPU to run the video output directly -- but the answer to your question is that yes, your results are very dependent on the system as much as the monitor.

You posted a generic question, which received a generic answer.  No one can answer definitively without knowing what model notebook you use.

You posted in the Inspiron notebook forum, though, so the assumption is that you have one or another of the Inspiron or G-series models.  If you're just looking for information about a monitor without regard to the system, you should have posted here:

https://www.dell.com/community/Monitors/bd-p/Monitors-Forum-f3529?ref=lithium_menu

neerav_d,

The performance of the U2415 should not change based on port used (HDMI 1/HDMI 2/DP). The performance should always be as stated in the online U2415 User's Guide. But, how it "looks" to your eye could be different based on the unknown GPU model and ports used. You will simply need to test it.

1920x1200 60Hz
Color gamut of 99% sRGB with an average Delta E < 3
High Dynamic Contrast Ratio (2,000,000:1)
16.78 million colors color depth
CIE1976 (91%), CIE 1931 (76%), and sRGB coverage 99% color gamut