I have a 16:9 Ultrasharp from the previous year, I believe it is the U2414h, but I could be mistaken. I was a little skeptical at first, because Ultrasharps are pretty expensive if you are used to buying the cheapest monitor that meets your criteria. Subjectively though, this monitor is amazing. The best thing I can say about it is that I almost regret buying it, as every other monitor looks terrible when placed next to it. Otherwise, I could look at the monitor all day without really thinking about it. It's like a really nice tool, in the sense that you almost forget you are using it because it does it's job so well.
For those of you unfamiliar with Dell monitors, the first letter is the model range. U is Ultrasharp, which generally are IPS displays and come from the factory with a certificate indicating the display has been calibrated, as well as stands with tilt, swivel, rotation and height adjustment. P is professional, which are generally very similar to the Ultrasharp displays, but without the exacting calibration, and the stands generally only have adjustable tilt and height. E (I think) is the third type, which is the kind of monitor you might get with your average computer. The stand generally only tilts.
The first two numbers following the letter indicate the size of the monitor, and the last two numbers indicate the year the monitor was released. I believe trailing letters are used when disambiguation is needed. So a U2414h is a 24" monitor released in 2014, and the h indicates it's the 1080p model rather than the 1200p model. The U2415 was released the following year.
Honestly, it's basically a recollection of some information on one of the /r/buildapcsales threads on reddit. The Dell Outlet has monitors on sale all the time, and they generally either seem to fit in to one of two classifications: refurb or coming off a lease (which is probably technically a refurb as well). The information provided is generally lacking unless the monitor is being also a model Dell is currently selling new. Dell tends to release monitors to the outlet in batches, which generally inspires someone to make a post on /r/buildapcsales. Someone then inevitably asks what the difference is between the product numbers.
Honestly, if you ever need to figure out what the difference is between product numbers, searching for it on google using "site:reddit.com" or "site:reddit.com/r/relatedsubreddit" is a pretty good way of learning what they mean. Otherwise you only get results for out of stock listings on Newegg or Amazon.
(I'd highly recommend reading the TFT central reviews of monitors. I learned a lot about monitors from them.)
One thing I didn't mention is that Ultrasharps and the Professional models tend to have VESA mounts, whereas the standard line doesn't. If you have a mount for your monitors, I'd probably go with the Professional line, since they have the VESA mount, and you aren't paying the extra money for the really nice stand.
However, if you don't have a mount, the Ultrasharp stand is amazing. I think it's worth the price premium for the stand alone. The base rotates, the monitor can rotate 90 degrees in either direction, the screen tilts, and the height is adjustable as well. The stand is literally perfectly designed. Adjusting the monitor doesn't require any tools, but unlike a lot of other stands (I'm looking at you desk lamp) the monitor will not move unless you are intentionally moving it. It moves smoothly once you start adjusting the monitor though, so you never have the issue where you overshoot your intended adjustment several times.
The stand is nicely weighted too, so the monitor tends to stay in place while manipulating it as well. The only adjustment that isn't completely smooth is the screen tilt. The tilt is a bit solid, and I just end up rocking the monitor back and forth if I try adjusting the monitor with one hand. I need to use a hand at the top of the monitor and one at the bottom to adjust it.
The height and tilt adjustment alone is worth it for me, since I'm pretty tall and have trouble getting my monitors in the right place.
One other thing, I believe the Ultrasharp models and Professional models are much more likely to have a matte finish on them. I'm rather fond of a matte finish, but I know people who prefer their computers to have a glossy finish.
One last point about my monitor in particular -- the bezel is advertised as being quite thin, but that's a bit misleading because there is a slight black area around the edge of the screen. I'm not in front of that monitor right now, so I can't comment on exactly how far it extends, but it's much wider than the actual plastic of the bezel. It doesn't bother me in the least, but if you put several next to each other expecting to have less than a couple of mm between each screen, I could understand getting upset.
For those of you unfamiliar with Dell monitors, the first letter is the model range. U is Ultrasharp, which generally are IPS displays and come from the factory with a certificate indicating the display has been calibrated, as well as stands with tilt, swivel, rotation and height adjustment. P is professional, which are generally very similar to the Ultrasharp displays, but without the exacting calibration, and the stands generally only have adjustable tilt and height. E (I think) is the third type, which is the kind of monitor you might get with your average computer. The stand generally only tilts.
The first two numbers following the letter indicate the size of the monitor, and the last two numbers indicate the year the monitor was released. I believe trailing letters are used when disambiguation is needed. So a U2414h is a 24" monitor released in 2014, and the h indicates it's the 1080p model rather than the 1200p model. The U2415 was released the following year.