Steve.
Both fin and wing keels are fine on a Catalina 30. Yes, a fin keel will sail a bit better, but not enough to make a big difference. If you sail in an area with shallow water, the wing keel offers a lot of advantages. If water depth is not an issue, go with either. Of bigger importance is the engine size. On that boat (I owned one for about 10 years), the larger engine is very (very) nice. Not only does it push the boat faster, but it will push you into a head wind/swell with much more authority! If one boat has better electronics and other stuff you like, that is a big consideration. How important is the cockpit shape? That's something you can't change.
Buy the boat that has the best match for your personal preferences. Good luck, and let us know what you do!