What is your intended use of this setup ?
With a 30" middle and two 24" sides there will be a difference in the resolutions since the 30" will have a native res. of 2560x1600 and the two sides will have 1920x1080. This will be ok for productivity and web browsing and movies but might be a problem with gaming.
The other setup would be all 1920x1080 so no problem there.
So depending on what your plans are I would think that three 24" monitors would be a good setup.
I guess that it's up for debate on which way would be better and my opinion the best option for gaming it to have a 30" monitor for playing the game on and then have a smaller size 24" to 27" for a side monitor to have things open on the side one like resource monitors or temp windows and maybe a browser open to use or whatever you want. I have always liked the idea of three monitors set up for gaming but don't know if I think it's better then a 30" , it's the bezels that make me think it wouldn't be that good where with the 30" you have a lot of size with no bezels. I guess I would have to try a three screen setup to see.
If they were able to make a wide screen that was the size of three 24" monitors as one continuous screen I would be the first to sign up.