There's capability and then there is design
I suppose most any boat could be blue-water "capable" as long as it doesn't hit seriously adverse conditions along its way. After all, there are some out there I know who have single-handedly raced an Olson 30 (a 3,000 lb boat), or similar class, to Hawaii from San Francisco. Certainly, that boat is "blue-water capable" since it crossed approx. 2,000 n.mi. of open sea far from land over 6,000 meters of ocean depth and didn't get sunk. People, I've heard tell of, have circumnavigated in a Catalina 27!! So, there is "blue-water capability" there as well. Actually, I'm amazed at the classes of yachts that some people will take off in and sail to distant places across the "blue water." So, your question might really be one as to the difference between boats designed for extensive blue-water cruising versus those that are designed for perhaps only close-in coastal cruising. But what is extensive "blue-water cruising?" Do we mean relatively short passages of perhaps only 500 to 1000 n.mi. in decent weather along a coast line? What difference is there between cruising 100 n.mi. down your local coast, or one 1000 n.mi. away, except perhaps for the availability of close harbor? Is a couple of two-week passages per year between two points across open sea "extensive?" I suppose the real question is what boat do you want to be in when the 60-knot wind and 35' seas, and larger rogues, come and roll you over a couple of times, or when you drop 10-20 feet off a steep wave and land on your beams end. Will the boat crack like an egg shell and sink, or stove in a port light and half-fill with water? It's all about risk versus $$$ and what you're willing to accept. So, yes, a more strongly-built "blue-water" cruiser will hold up much better over the long haul; as the fellow said, it depends on what you're going to do (where you're going to go) with your boat.