Try and test one out or at least get to a shop and see one.
I had a DGM 1440p monitor stolen and after using a 24" old Dell for a while I decided to go for a 21:9 LG 2560x1080 monitor. I liked it and it was indeed a beautiful monitor with a great and vibrant screen. But I just could not get used to the lack of vertical height, being very slightly less than my 24" and much less than the 27".
There was no way I could afford the 34" higher resolution LG and so I decided to go back to a 27" 1440p. There are aspects that I do miss from the beautiful 21:9 but overall I feel better with a 16:9 27" and I'm glad that I made the return. The BenQ 27" seems slightly better in picture over that of the LG but I do not use a monitor for films generally and so that is not important to me, prefer our larger Plasma for that.
For many people it works out well with the 21:9 choice but try your best to take a look and test one out first.
Regardless of which monitor you go for deal with a retailer where returns are easily accommodated, after needing to return two AOC 1440p monitors I know the value of that.
Good luck.