Tough decision, but try the power steering. It makes maneuvering the tractor much quicker and when you’re older like me results in less pain. I skipped the X5xx series going from my X360 (X390 now) and went to the X738 because I found one on Craigslist. What you find on the larger heavier tractors is they are more stable on steeper slopes. I mow the lower part of my ditch easily. The upper part of the bank is from 20 to 45 degrees and I mow up it. Once the tires crest the hill, I have to raise the deck or scalp the grass or stop. The 54” deck is too big for my yard, but great for mowing the soccer field at the local Christian school. A larger deck can help by keeping the tractor farther away from things like buildings or fences.
What helps in the decision is whether your wife or kids will be using it and how big or strong they are, as well as how old you are. Even on the flat soccer field, I find the power steering a benefit when I turn around on the end to go back across the field. If I mow around the field, I can make square corners in about 3 seconds, which is coming close to a zero turn. Don’t miss the fact that the larger tractors also are heavier which may be a problem on soft ground, but sooo much better ride on rough ground, which translates to less pain as you age/less medicine for the pain that it induces.
My friend had a Cub Cadet 54” deck with manual steering until he had a shoulder replaced in September, a few years ago. I drove it for him and didn’t think twice about it, even at 68. The next Spring he took it out and the very first time he felt it hurt his shoulder, so he went tractor shopping for power steering. He is still blown away by how easy he can maneuver his Kubota BX2380 54” deck around his tree, flower, stuff filled lawn every time he uses it and loves it when he tows his Cyclone Rake XL around his leaf filled lawn, even at 80 years old. He can get it into places he never could with his Cub Cadet.
All this to say, there are other factors that make one tractor choice better for you or whoever is using it. Can you fit it everywhere you want to? How does it fit whoever and everyone driving it? How comfortable is the ride? How much pain and fatigue do you want to tolerate? How safe is it to use throughout the lawn? Will you need bigger to do more? All questions that affect your choice or you resolve yourself to trade as requirements change.
Don’t get too hung up on the safety feature of pushing a button to mow in reverse. You can also lift the deck engage switch to do the same thing and both only have to be done until you start moving backwards, then they can be released until the tractor moves forward again. Don’t discount lightly used. All four tractors I’ve owned were used.