badadim...do a search on bluewater boats here...there are thousands of posts on the subject. The short answer is that they are built to take the constant pounding of the ocean and everything is overbuilt...that is why they cost 2-3 times as much per foot as the production boats you've listed. I've owned a number of production boats and one blue water boat...there is no comparison at sea. You can buy 27' bluewater boats...so it is not a size thing...it is a build quality thing.
There is NO DOUBT that MANY production boats have crossed oceans. My view is that if adults want to do that understanding the increased risks it is their right. When kids are involved I become a bit more vocal.