Well, according to that site mine would be like this.
http://www.displaywars.com/24-inch-16x10-vs-34-inch-21x9
Should maybe mentioned the Dell is 16x10 not 16x9's, since I see it makes a little bit difference.
In your question regarding the 4 monitors, there is Multi Stream Transport Hub that you could use, since say a 980 or a Fury can support 3 DP's you would only need a 1 for 2 Hub.. I got a 1 to 4 DP hub I bought some time ago, worked fine driving the 29'' and 3 Dell's from a 290... as long you not playing games with all 4 running.. lol .. I guessing a Fury or a 980Ti might be enough to drive 4 x 29'', if what you doing is not to taxing on the cards, like gaming.