Well, they only thing they are good for...NVR.
myDLink app sucks when you have multiple cameras, and my NAS will only allow two IP cameras without adding an additional subscription for camera licenses.
Honestly, I think that the 312L is newer (yes, I realize it doesn't make sense for a naming convention, D-Link sucks at that) because it has a HDMI port and multiple USB ports.
I see no advantage of the 322L over the 312L except for more storage...which shouldn't be an issue..