Some nice mowers you have narrowed down too. I am in the middle of this sort of decision myself, though I am looking at smaller rigs a few levels down in price.
Gravely and Grasshopper I have not looked at. The closest Gravely dealer is 1.5hrs away, so just not even an option. Grosshopper is even farther so I cannot help there. Both brands I hear very good reviews about.
As to the Ferris suspension not seeming special. Getting a feel for what the suspension will do is difficult, as most places will have all smooth ground, grass ,etc. to test in. Not saying they are hiding how their rig rides, but I doubt most buyers have super rough lawns to deal with so why would a store intentionally have them ride on rough ground and beat up their demo/floor units. To feel how the suspension really helps you need to get really rough/uneven ground. I am talking borderline potholed gravel roads, stuff you would have difficulty riding a bike on or would only dive your car at 15mph on due to roughness/bouncing. Then compare the ferris to others.
That may not be an issue for a great many if not most people and may have zero need in your case. If you have relatively flat and smooth ground the benefit of the suspension will be lost on you to a great extent. If you are having to mow slow for with your current rig for some reason other than ride you may not realize how rough your property really is, and when you get going zero turn speeds could make it pronounced. How rough is the new property? It may be flat, but the actual ground could be ripely, have unseen holes, divits rough spots. You may wish to wait to get a mower until you can get there and do an real onsite test with your existing equipment with regards to speed and smoothness. This may not really be something you can figure out by a walk thru unfortunately, unless it is super uneven, a rolling tire will expose roughness more. While other mowers may not have the full suspension, they have really good seats these days which may be more than enough for your needs.
Best thing I can recommend is find out about your property and then make a list of features that are important to you. Auto parking brake? dial deck eight adjustments, bagging, mulching (don't forget the cost of accy's in budget calculations)
8-9" of loss in deck size with the Grasshopper is pretty significant, it is more than 10% difference. BUT if that tilt up deck makes it easier to store and even more importantly easy to clean so you will continue to clean it all the time then that extra time making more passes mowing could be significantly offset from less time cleaning and more importantly wear and tear on the deck from grass build up. 10min clean off after mowing vs 30+ putting out a jack etc adds up and could make you more likely to clean every time, It could add years of trouble free service, that has real monetary value to it.