Both of these boats are good boats, the question is whether they match your needs well. The 31 was one of the few Cape Dory's that was not an Alberg
design although from a distance it looks quite similar to other models. Some people would consider this boat pretty small for offshore
work although it would make a nice coastal cruiser for anyone willing to live fairly simply. I do not have any real sailing experience aboard the 31 so I really don't feel qualified to comment on it further. These boats have been sailed blue water
so it can be done.
There are actually 2 33's, the 33 and the 330. The 330 is probably my favorite Cape Dory in this size range and if I had to pick between the 31 and the 33, it would be my choice. They are well constructed and sail nicely although they still pitch
and roll more than a lot of the modern boats but they do it in a gentle way usually. Several 33's have been sailed long distances and the reports that I have heard have always been good.
I would suggest that you investigate the Cape Dory Owners association and its forum if you haven't Welcome to the Cape Dory Sailboat Owners Association's Home Page
. The forum is really good and you will find many owners of both models including ones who have sailed them long distances.
There are certainly other boats out there capable of doing what you want to do so don't limit your search too much. If you want a smaller boat for your intended cruising, then both of these would be a decent choice.