Your Mac or MacBook's display is already gorgeous. If you're in the market for a second display or something larger than what you have, a 4K monitor is a huge step in the right direction, so you can try and maintain the same level of definition.
Dell P2715Q
The Dell P2715Q (about $400 is a feature-laden monitor that can tilt and swivel to any orientation you desire, making it excellent for an workstation configuration – if it's a second monitor, it can pivot from landscape to a portrait orientation! The IPS panel makes for excellent viewing at just about any angle and if you're into connecting peripherals, it has just about every port you could need (minus USB-C).
Why the Dell P2715Q is the best
Versatility and performance in a 27-inch package.
Out of the gate, the best part of the P2715Q is its IPS (in-plane switching) panel. These work by orienting the liquid crystal molecules horizontally, creating richer color and allowing for great side-viewing. So if you need to swivel your monitor because of the space on your desk, it'll still look as great as if you were looking at it head-on.
This monitor features a 9ms response time. Can you count 9 milliseconds? I can't, and your eyes won't be able to either. That means that from the time you click on an icon or move your mouse all the way across the screen, the response time will be less than a hundredth of a second. To put that into perspective, it takes 300 to 400 milliseconds to blink your eyes.
The P2715Q was made to be connected to stuff – it has 4 USB 3.0 Type A ports, a USB 3.0 Type B port, a DisplayPort, a mini DisplayPort, a DisplayPort output port, and an audio line out. The only thing it's really missing is USB-C, but that's nowhere near a necessity for right now. That being said, for under $400, this one's incredibly hard to beat.
LG 27UD88
LG is one of the best names in TVs and their monitors are no different. The 27UD88 is definitely your best choice if you're looking to future-proof your setup, since it features USB-C, which is steadily picking up steam on its way to become the gold standard. This monitor features a gorgeous IPS panel with such rich color that it covers over 99% of the sRGB color space – if you're editing photos or video all day, this one's for you. You may have to spend a little more now (around $650), but you'll save yourself some cash in the long run.
ASUS PB287Q
The ASUS PB287Q has a TN panel instead of an IPS panel, meaning that its color reproduction isn't amazing, but its response time is only 1ms meaning that you'll notice no lag in performance whatsoever – if you perform an action on your keyboard or move your mouse, you see it on the monitor in real time. The PB287Q also features picture-in-picture and picture-by-picture, which allows you to view content from two sources at the same time. If you've got a lot to do all at once, the PB287Q will be more than able to keep up with you. Plus, you can find it for under $400!
LG 27UD68P
LG's other awesome 4K monitor, the less expensive (about $400) UD68P isn't exactly future-proof, but it's one of the best monitors you can buy for right now. It has 2 HDMI ports, a DisplayPort, and a headphone jack. It could do with USB and optical audio would be nice, but this'll still get the job done (with a Thunderbolt/HDMI adapter).
The UD68P also has an IPS panel, which means awesome viewing angles and deep colors. It sports a gray-to-gray response time of just 5ms, so it's not perfect for gaming, but it's just great for most people. If you buy it on Amazon from Beach Camera, you'll get free shipping, a screen cleaning kit, a 6-outlet power bar, and two 6-foot HDMI cables. All for about $400.
BenQ PD3200U
BenQ's 32-inch PD00U might be pretty expensive (about $800), but it's packed with features that pros will love, like an IPS panel for awesome viewing angles, awesome color performance, which is perfect for video editors and all other types of post-production work. It also has an "Animation Mode," which brightens dark areas without overexposing bright spots to help you work with the intricate details.
The PD00U has 2 HDMI ports, 1 DisplayPort, 1 Mini DisplayPort, a USB 3.0 hub with 4 downstream ports and 1 upstream port, and an SD card reader (yay, newer MacBook Pro users!). It's expensive, but if you're pro and need to be hella productive, it's worth it.
Updated April 2018: The Dell P2715Q is still the best 4K monitor you can get right now, and I've added LG's UD68P, which is a great budget option for most people, as well as BenQ's PD3200U, which is a beast for performance and features.
