Similar aged boats, one lightly used and one proven.. but aside from that they are quite different in other aspects. The 31 has a masthead 'B&R' rig with severely swept spreaders, the 30 IIRC has a more conventional, nicely proportioned fractional rig. This will mean smaller headsails and easier handling esp tacking and if a spinnaker is included. This might suit your intended use better.
In many cases boats recently returned from major offshore ventures are long overdue for a serious refit.. this may or may not be the case here...
Interior wise I wouldn't expect to see much difference, but the 30 is of the 'next generation' design from Hunter, leading to the rest of the Legend line (33.5, 35.5, 37.5, 40.5) Either will likely have an iron keel - if so that will be a wash.
I guess it's going to come down to which one 'speaks' to you, which layout you prefer and how much stock you put into 'proven' vs 'lightly used'... either can be good or bad.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)