4K back then was either too expensive or the quality too poor. I’d seriously look at 4K these days, but having a single UW monitor is nice, you can maximise a spreadsheet over the whole desktop, not have to manually drag the window size over both monitors and you don’t have a bar in the middle, where the bezels are.
I have used some UltraSharp and non-US Dell monitors. For a bit of word processing or Excel, the non-US models are fine. If you are going to be doing video or photo work or spend a long time in front of the monitor, I’d go for the US model, if it was my money. But at work, the cheaper options have the same resolution, so that extra for a US model is “wasted”, because you don’t get anything for it (bigger size, better resolution). I currently have to P 24" FullHD monitors at work and the quality to my 34" US UW is night and day, but the extra resolution also helps make the 24" Ps look grainy, but the colours are also a bit washed out in comparison.
If you can stretch to it, I’d say go with an UltraSharp, given the choice, but even the non-US models are “good enough”, if money is tight.