But you really shouldn't take financing/initial cost out of the equation totally, because if you buy the new Catalina, all that money is gone; if you buy the $30K Tartan, you would have alot of cash left over to invest wisely, which could pay your annual mooring costs and some of the maintenance.
People have done similar analysis on buying a new car vs. buying a good used car, and financially, the used car usually wins out. But people still buy new cars for various reasons. I think the same holds true for boats--a used boat in good condition will likely cost less in the long run--you save on initial cost, insurance, fitting out/customization cost, depreciation. Once you get the used boat into the kind of shape you want, the annual maintenance cost will likely only be a bit higher to replace the odd pump or fitting. You may face an added initial cost for new sails or engine on the used boat, but I think will still come out ahead.