I had an opportunity to view / play two boxes
2560 x 1440 144 hz IPS w/ G-Sync & ULMB and twin 970s
3440 x 1440 60 hz TN w/ G-Sync (no ULMB) and twin 980 Tis
The curved wide screen was cool.... for a while, but going back to the 1440p made you suddenly aware of the better colors and lack of motion blur.
Used to be that 3440 was somewhat frustrating as early on fewer game vendors supported this resolution and scaling or other options were less than satisfying. This situation continues to improve over time.
But when it comes down to a choice of 3440 or ULMB, I like ULMB. If I was to get a 3440, this wud be the one ... tho response tims range from 6 - 15 and 9.2 lag is about 3 times that of the betetr 1440p panels...