I spent weeks talking to several dealers about the same decision, though I was going from a JD 2305 so the 2320 would have been just one marginal step up. The 2320 was actually my gut choice for my needs but the 2520 gave me some growing room. It has much faster hydraulics, dual hydraulic pumps, a more robust transmission, direct injection, and more ground clearance. If I had flat land, I could have used it to mow, but our slopes forced me to split the task off to a dedicated mower by going with the 2520. With the 2320, I probably would have forced using it as a mower and possibly regretted it. Even though I received a lot of advice that the 2520 could be used to mow my land, I knew better and thankfully listened to my intuition. That machine is a monster on grass with its big R4 tires (relative to the 2305).
There isn't really a huge practical difference between these two machines. It's all nuance. Everyone's input is helpful, but only you can ultimately make the decision based on your settings, tasks to be done, economics, tolerance on availability, etc.
In any case, welcome to Green!:thumbup1gif: