Hello Walkyrie,
As far as I have read on many forums, you will get many different advices about which organ has the best sound.
If I may, I would tell you some "research tips":
About modern electronic organs that are brand new nowadays: know that there are two concurrent technologies to create the note: sampling and synthesis. For example, Johannus uses sampling technology, as well as up-to-now Viscount models (i.e. except the "Physis" models).
In fact, for those using sampling, you will find arguments are about the length of samples, the number of samples, and some modifications to simulate "wind effect", etc...
For those using modelling or synthesis, you will find different hardware or software used (Musicom, customed musicom software or (it seems) completely new and patented Physis modelling for Viscount). Please note also that, for the same brand (for example Viscount), expanders can be modelling sound whereas organs use samples.
Those who choose pipe modelling technology will say that only this technology can make you feel the "ensemble sound", with pipes influencing each others when played simultaneously. However, it seems that "samples addicts" have found also the way to model this with samples.
I don't know which one is the best. Even if you were sure about the number of keyboards and pedalboard disposition, about the stops you want, there are also so many things that must be taken into account that it will be difficult to choose: woodwork used for the console, amplifiers and speakers numbers, speakers disposition, keyboard quality...
If you can listen to these different organs, it will be better!