I just went from a riding mower to a zero turn. I have a bit more property than you (7.15 acres), but can easily say that the riding mower seemed ok at first, but I ended up tearing my rotator cuff, and that forced me to spend the extra. Now, I can honestly say how bad the riding mower was. I bought a cub cadet after sitting on several others, and it is, by far, much more comfortable for me. Mowing is far easier, getting a nice finish fast is a huge thing.
Far less need of manual weed eating since I can get in and around things pretty close. I have many obstacles to work around, so that is also a factor for me. I chose a 54", but could have gone bigger, I would not advise smaller since having the cutting edges outside of the wheel base is a massive benefit even on a smaller yard.
I was nervous about driving one, but it took me about 5 minutes of getting used to it, now I can mow quite fast, and with 3 cutting blades, it cuts well fast! 7mph is fast on one, and the fact it CAN do a good job at that speed is pretty impressive