S2719DC vs S2719DM?

@Ibxx0402  When I can't figure out the differences between two displays that seem similar, I look at their manual, which always contains a lot more information about specs and capabilities.  You can find the manuals for both of these displays at support.dell.com by just searching the model name and then going to the Documentation section.

I don't see why you wouldn't be able to use HDR and FreeSync simultaneously, assuming your GPU supported both of course.  Using HDR would consume more bandwidth than an equivalent SDR signal at the same resolution and refresh rate, so that might limit your MAX refresh rate, but sending an HDR signal shouldn't affect your ability to use FreeSync's variable refresh rate technology -- again unless there might be some limitation on the GPU side.

@Ibxx0402  I agree that at 27" 1440p vs. 4K is unlikely to be very noticeable.  However, if you're buying specifically for HDR, there are very few PC displays I would recommend at all right now.  The issue is that good HDR requires displays to be able to achieve very high peak brightness levels, and the vast majority of PC displays just can't get there now.  Even many HDR TVs can't.  And the PC displays and TVs that CAN get there are definitely pricey.  On the PC display side, VESA has created the DisplayHDR certification tiers to help consumers quantify HDR performance and differentiate displays, so you might want to look at those.  Most displays I've seen either don't have any certification or only meet DisplayHDR 400 standards, which is their lowest-end certification.

As for 60 Hz, it does seem like the next generation consoles will support 120 Hz.  I'm sure they won't REQUIRE it, but if that's something you want, you may want to hold off.  Another reason to hold off is that HDMI 2.1 introduced support for Variable Refresh Rate (basically an industry-wide standard for what G-Sync and FreeSync do), which can be even better than just having a static high refresh rate.  So you might want to wait to see displays that support HDMI 2.1, including VRR, if you'll be using it mostly for gaming.  Of course the tech world will always have something better coming if you wait a bit longer, and at some point you have to buy something.  But again, if you specifically want HDR, plan to spend a lot more than what these displays cost in order to get it properly.  If you buy "cheap HDR", it won't look very good, and you might have done better overall by spending that money on a different display entirely, or just saving the money.

@jphughan thanks again for the reply, I didn't know that the new HDMI 2.1 would bring VVR support, I only thought it would make it possible to show 4k 120Hz and 8k 60Hz. it looks like I need to wait until a wider range of monitors has HDMI 2.1, to get a better display. Maybe the wait will bring better HDR at an acceptable price point.  

@jphughan thanks for the reply, I will be looking through the manuals to see if I can spot a difference between the two.

I plan on using the monitor with my PlayStation, so I can see the beautiful HDR content the games provide. I also think the monitor is quite future proof since I don't think I can see too much of a difference between 4k and 1440p at 27 inches. though I am not sure if 60 Hz is enough for the next generation of console gaming. 

@Ibxx0402  Happy to help.  I believe that even with HDMI 2.1, support for VRR is still optional though, so make sure that the display specifically supports that feature if it's important to you.  And then of course it remains to be seen whether the next generation consoles will support it.  I bet they will though, given that gaming is the major use case for that feature.  HDMI 2.1 also adds some low latency Game Mode.  I haven't read about it in detail, but I think it basically puts your TV into its lowest latency mode automatically without you having to specifically choose that -- and then when you're not gaming, it can go back to a more color-accurate profile like Cinema that might involve more processing.  Again, I think that's what it is.