MBP to Dual External Monitors - 1 has horrible resolution

[Hankcah]

On the new MBP Space Gray, and like to dock it under one monitor. Both are HDMI connections. One USB-C is an Apple dongle and the other is an Anker dongle.

The problem is -- whenever I hook them up, only ONE monitor has the amazing resolution, and the other goes to potato quality. It doesn't matter which cable I hook up first, the order of cables, or which dongle I use.

My Samsung 28inch is fine, but the problematic one seems to be Dell S2740L. The only spec I see on it, in SysPrefs > Displays is the Color Profile HD 709-A. Are there drivers for this monitor for Mac anywhere to tweak the settings more?

When I just have the Dell monitor setup then it looks completely fine and nice resolution. So I don't buy that it's the monitor, even though there are limitations.

 

[Fishrrman]

Looking at the image you posted above (of the displays pref pane), it looks like the MacBook is "seeing" the Dell "as if it were a tv", rather than as another computer display.

What tips one off to this is the fact that the "underscan" control is present.
You don't see this available with the other display.

If you connect ONLY the Dell, using the same connecting cable as you would use to the U28E590, and then look at the displays pref pane, is the "underscan" slider still present?

 

[robvas]

According to Google the Samsung monitor is 3840x2160 and the Dell is only 1920x1080

Which MBP do you have, exactly?

 

[DeltaMac]

And, yes, there will be a large difference between the two displays, with the Dell at full HD, and the Samsung at 4K UHD resolution. They will always appear different in quality.

Another choice is to use the DVI connector on the Dell, not HDMI. That may force it to recognize the display as a monitor, and not a TV.
Check with the Dell in "scaled" settings. Can you set that for a resolution that is better for you?

 

[Fishrrman]

The OP mentioned that when he connected the Dell "alone", it looked much better.

I'm wondering if he used a different cable, etc. -- and by doing so, had the Dell "appear" to the Mac as a computer monitor, and NOT "as a tv". The "overscan" in the pic posted above gives that away.

OP -- have you tried tinkering with the "overscan" slider in the displays pref pane?
Does it change anything?