It really depends on what you are going to be doing (which apps). I have both set-ups (sort of). I have two 24" Dells, two 30" Dells and two 30" ACDs. The 24s are not great if you have applications which are best with extra vertical height. The 30" is much better for that. However, you give up some horizontal width. If that is more important, then the 24's are better.