I have a 27" (2560x1440) and 26" (1920x1200). Since they are different aspect rations and densities, it is a little but of a weird transition... even though they are about the same height.
If anyone interested, the Assault Mech (https://www.assetstore.unity3d.com/en/#!/content/25929) will be discounted 50% from the original price of $90 on June 27, 2015. \o/
@Shrike: Yes thats an opinion,too. Thanks for that :) But actually i have only one monitor :( sometimes that disturbs. But i got used to it. And its 27" ^^