well. i have money to spend and previously i was thinking of changing my dual 21.5inch setup to a larger dual 27inch setup.

so then i realized, if i were to get both 1080p monitors that would Not give me more screen real estate, so whats the point other than having a larger display for movies/games if i cant fit more stuff onto my desktop.
Im also concerned if since its larger, can we really feel the difference in the clarity seeing as how 21 inch and 27 inch have the same amount of pixels would it make the 27inch blurry-er/ ugly

then i thought about getting a 1440p display. but graphic card only 750ti, tapi i also dont play alot of hardcore games on PC since i use my ps4 for that. so now im slightly torn on what to get
but generally i was looking into the dell S2715H.

any thoughts?

Yes, you may if looking at short distance, but not noticeable looking from far further.

Just like those large LCD TV, if you go closer to the screen, especially those not full HD one, but with large in size, you see blur image if walk close to the TV.

Having said that, the difference between 27" and 24" won't be too significant, we don't need rocket science to know if at same resolution, 24" will be sharper due to tighter dot pitch.
But 27" will have large text at native resolution that make text more ease to read upon.
I would say 24" is about sweet spot for 1080p.

The large the screen, the tendency use may sit further.

So it is about preference.