...
I'm looking for a 27 inch display.
The Dell SE2717H seems okay to me. But it's 1080p. And costs $249.
...
" $300-400 gets you a low grade 1440p monitor".
So, should I get a 27 inch, 1080p Dell monitor, or a 27 inch, 1440p monitor? But I don't want to spend too much money on the display.
...
Well Ed, with monitors, quality costs $. Size and resolution cost $ as well. If you want all three together you should get something like a 1440p Dell 27" monitor. That will cost something more than $300.
The U2515H is around $300 but it is only a 25" display. If you go down in size to the 25" Dell, you don't have to settle for "low grade". You can get the desired 1440p resolution for less in something like the Acer G257HU but this $250 display is also only 25". (note: This Acer lacks the VESA mounting feature that most others have.)
Your planned uses do not sound very demanding. If you must have a 27" display then your choice is clear. Can you settle for a "low grade" 27" monitor? If not, you can pay the price for a quality 27" or decide to choose from a range of great 25" options.