Hello Stefan. I went through this a while ago and Ive got to say that I am unable to justify the cost increase. Compared to my 1.25" eyepieces, the only advantage I found was that I had more real estate around my objects, it didn't make them any better, brighter or larger etc. If you have really dark skies and want to view extended objects, it may help. If you have a large aperture telescope that makes the objects appear bigger in your eyepiece, the extended field may help there as well.
I love my very beautiful 2" WO dielctric diagonal, but for now, it's 1.25" for me.