I tested the 2305, 2320 and 2520 and then had all 3 lined up side by side. I bought the 2320.
The difference in price was about $2500 between the 2320 and 2520.
The $2500 would have bought me:
2.5 more hp
somewhat quicker hydraulics (i operated both machines), larger pump
2.2 more inches of wheelbase
an operators platform with a significant hump (2320 has flat operators station which is great because I have big feet)
1 gallon more fuel capacity
205 more pounds of weight
Same 3 pt hitch lift capacity
Same 2 range hydro trans
Same drawbar tongue capacity (562lbs)
Same electrical system
Same axle capacity, both front (1940lbs) and rear (2426lbs)
Same ground clearance
When I compared the specs, operated both machines and lined'em all up side by side I quickly realized that the $2500 could be better spent on attachments

rather than 2.5 more hp, a larger hydro pump and a gallon more fuel capacity.
Whatever you decide you cannot go wrong. They are both great machines.
HAve fun shopping.
JD 2320, JD X485,
AMF1010
Formerly owned:
JD 320 (great tractor)
2004 Cub Cadet 5234D/broken trans, broken front axle, etc...(124 hours)
2006 Cub Cadet 5234D (replacement)/unrepairable engine (10 hours)