The 20K boat looks like the better buy because of all the new gear.
Any good surveyor will know to check the keel bolts & bilge on a boat of this vintage and an email to the seller can confirm if the repair has been done.
Also ask about the rebuild. What did it entail, who did the work, what is their reputation? Does your surveyor know their work?
These boats are very comfortable and Barry raises good points about the refirgeration and stove. Look closely at modifications to the electrical system.
The differences between wing and fin keel are overstated. My C30 moves along in light air and so far no problems getting off minor groundings in sand in Barnegat Bay. The difference in how high she'll point will only be an issue if you race.
Check out this link to get an idea of the differences between Catalina 30 models and a lot of good general information about the boats.
International Catalina 30 Association
& C30 Yacht
Best of luck with whichever one you pick,