It's probably not so much 16x10 vs 16x9, but more 5760x1200 being tougher on video card performance than 5760x1080.
If you're picking new monitors and are considering those 24" Dells, might as well consider the P2310H too. It's the same resolution, only 1" smaller, but comes with native DP so you won't need the DP adapter, and can rotate portrait/landscape.
I bought 3 of those P2310H's and I love em. I had two 24" Dells before, and I really don't notice the size difference, but the flexibility, USB ports, and native DP are well worth it. When you have 3, you probably won't notice any difference. I work everyday on a single 24, and the 23s at home don't seem any smaller. Definitely recommend the P2310H. I got mine on sale from Dell for $185 each, and if you wait a little while you'll probably be able to get them for close to that.