U2722DE, questions

@ss98  If you haven't already, you might want to check out the U2722DE's manual here, which includes sections related to the KVM function -- although I admittedly didn't find a specific answer about the auto switch timing requirement, but then again I didn't check thoroughly.  Still, I really wouldn't recommend a conventional 16:9 display for frequent PBP, since that means you'll only have an 8:9 aspect ratio tile for each source, i.e. the tile will be taller than it is wide.  If you want to use PBP a lot, I'd consider at least a 21:9 ultrawide or better yet a 32:9 "super-ultrawide".  With that type of display, each tile becomes its own 16:9 display.  For example, Dell and Samsung make a 49" 32:9 display with a 5120x1440 resolution.  It is just a pair of 27" QHD displays side-by-side and fused together -- but when used in PBP mode, each source essentially gets its own 27" QHD display.

The data-only upstream USB-C port don't accept a video signal.  That's why it's a data-only port.  If you want to use a second laptop, you'll need to set up video and USB data paths separately using two separate cables -- and that laptop won't be able to draw power from the display.  You could for example use a USB-C to DisplayPort cable for video and a USB-C to USB-C or USB-C to USB-A cable for USB data.  Either way, make sure the latter cable is rated for USB 3.x Gen 2.  Many C to A and even C to C cables only support USB 2.0 because they're designed to be used primarily for charging devices, and another large portion only support 3.x Gen 1.  Also be aware that typical passive cables right now that support 3.x Gen 2 are limited to 1 meter / 3 feet, and C to A cables that support 3.x Gen 2 are especially rare because relatively few systems ever implemented 3.x Gen 2 support on their USB-A ports.  This all assumes you actually care about using the display's 3.x Gen 2 capability of course.  In fairness, it's not very widely supported among peripherals, or even systems for that matter, and now that USB4 has arrived, it may never see wide adoption.

Can't speak to brightness, but that information may become available as more reviews from outlets known for extensive testing get published.

@jphughan, thanks! I didn't think about aspect ratio in PbP, so based on your suggestion I looked around on Dell site and found these two (looking to get a Dell this time, ~35" is the max I could fit into my setup)

1. P3421W
2. U3421WE (don't really need the ethernet) - out of stock.

I'm assuming ~ $280 price difference is not just for few extra ports.  I'm fairly picky about screen quality. Did you happen to use both P & U series monitors?

@ss98  Happy to help!  Yes I use both P and U Series displays.  In many (most) cases, they share common panels.  The U Series displays often just have additional features not available on the P Series, or at least get those features earlier.  Here are some examples:

• Built-in Ethernet, as you noticed
• Built-in 3.5 mm audio output jack to pass audio received via HDMI/DP to speakers.  (PC sources can use USB audio, but devices like game consoles and media boxes typically can't.)
• Support for DP 1.4/HBR3 rather than 1.2/HBR2 (can enable more daisy chain scenarios)
• Support for USB-C Prioritization customization (half-bandwidth video + USB 3.x or full-bandwidth video + USB 2.0.  This flexibility comes into play with daisy chaining.)
• Support for higher USB PD power output
• Support for USB 3.x Gen 2 (10 Gbps) rather than just Gen 1 (5 Gbps) or sometimes a mixture of Gen 1 and USB 2.0.  Sometimes U Series displays also have high power output USB ports for fast charging devices.
• USB-C downstream port (to connect USB-C peripherals to the display)

But if you don't care about those types of features, then equivalent P and U Series displays very often use the same panels.  One way to get a sense of whether that's the case is to check the manuals of both displays of interest and check the specs of the actual panel, such as viewing angle, response time, and such.  They are often identical.  And the rest of the manual will also give you an idea of where the differences are in terms of other features.

@jphughan, thanks again! very informative stuff. Btw, after checking my available space again, I went ahead and ordered a U2722DE. I'll let you guys know about the auto kvm and minimum brightness. I plan to make some more room to add another 27" after few months. I liked that UP2716D Dell's currently selling and already started scratching my head - should I get another 22DE or 16D? Both are daisy chain capable, do you think different models could cause issue? 22DE has DP 1.4, but 16D user guide apparently doesn't list its DP version. 16D, despite being a pretty old model, still comes with a better panel (based on my spec comparison from their guides). So wanted to try something different next time if they can be chained together properly.

Btw, I'm assuming all these high speed USB ports will matter only if the source PC usb port supports same bandwidth. And then why would you want to pass through the monitor ports anyway instead of connecting directly to the pc/laptop? I'm not complaining about Dell putting those good stuff in any way, just wanted to understand use cases.

@ss98  Different models don't cause a problem with daisy chaining, or at least they shouldn't.  The tech world always has occurrences of problems that shouldn't exist but do anyway, but that's not the norm.  A 2016 model year display would be DP 1.2.  And yes, the 16D has a better panel because it's a UP series display, not a U series display.  It's geared specifically at people doing color-sensitive work and therefor has a wider gamut and more ability to be calibrated.  It's also significantly more expensive, or at least it was back then.

Yes, if you want USB ports built into the display to run at USB 3.x Gen 1, for example, you need a USB 3.x Gen 1 data path back to your source system.  But that isn't difficult to achieve.  As to why people would want to connect USB peripherals to their display, once again it's a matter of convenience.  If you have a bunch of USB peripherals connected to your display and only one cable from the display to your laptop, that's one cable you have to connect/disconnect as you come and go with your laptop, rather than a bunch of individual USB cables.  Maybe your laptop doesn't even have very many USB ports, in which case the display might save you having to buy a separate USB hub.  And if you'll be using a display with a KVM function, then having your keyboard and mouse connected to the display means the KVM function can switch those peripherals back and forth between source PCs as needed, otherwise you'd have to physically move the keyboard and mouse between source PCs.

@ss98  No, that won't work.  Even if you switch the Bluetooth adapter between source systems, the actual Bluetooth pairing information is stored and managed by the OS, so you'd end up having to pair your keyboard with each system (through the adapter) each time.  Logitech's Unifying Receiver works differently in that the pairing is actually managed within the adapter itself, so in that case moving the receiver back and forth, either physically or by switching between source systems, will allow the paired peripherals to "follow" the adapter automatically.  But regular Bluetooth adapters do not work that way.

Guys, Received the monitor already - shipping was fast! Thanks, Dell.

So 

1.  Minimum brightness is actually pretty good. I'm very happy. This brightness can actually be further reduced from the intel's graphics control panel (which allows to go below 0) on my laptop.

2. Auto KVM switch actually works as I expected in my first post. Few things - enable 'auto kvm switching' on both laptops through Dell display manager (otherwise it'll be unidirectional :)) - also remember the 3 second rule. 

3. While KVM is all good, it doesn't fill the whole screen of this non-wide monitor in PbP mode as @jphughan already mentioned. Maybe there is a way around that - I just don't know yet. However, the input switch shortcut key is more awesome (again - enable it on both source PC/laptops through DMM). This monitor looks amazing when I used it in regular non-PbP mode with my 3 laptops. They all have different resolutions. The best clarity came out when I set the external monitor's resolution to its native QHD resolution (one of my laptops set to its own native resolution by default).

Hope this helps.