It looks as though it's those damn "open motorboats" followed by personal watercraft, cabin motorboat, canoe/kayak and "pontoon", that have the highest casualty numbers:
Click on downloading 2012 only, it's very long but the interesting pages (to me) are pages 6, 7, and 41, which are the Executive Summary (we executives can't be bothered to read long stuff) and the "Accidents by vessel type" page.
Good news!! deaths down by 13% over previous year.
No surprises--operator inattention and inexperience are the leading causes, then lookout, machinery failure, speed, navrules violation, alcohol use, wake, weather/hazardous waters, in that order. Alcohol use though 7th place, was by far the leading cause of death, double the next leader.
Total deaths 651, 286 of which in from open motorboat, 58 PWC, 55 cabin motorboat, 52 canoe, 44 pontoon, then it drops off. 3 types of sailboats (auxiliary, sail only, and "unknown") combined for 27.
There may be some page in there that tells you a ratio of deaths to the type of boat, but I suspect the sailboat crowd comes in safer than the bad actors in those open motorboats......
Perhaps you could ask your insurance company. They probably look at these numbers much more carefully than anyone else.
Now, that said, there are accidents caused by recreational craft to commercial vessels that don't show in the recreational stats. I handled one such at work last year. Gulf intracoastal waterway on a Sunday in Louisiana, two oil barge (loaded!) tows strung out in front of their towboats, approaching each other with a radio-agreed meeting arrangement when three idiot water skiiers towed by an (unidentified, and not for lack of trying) idiot ski boat with an idiot PWC tagging along, all overtook one of the tows then cut in front, then had their skiiers suddenly become idiot swimmers in front of both tows.
Tows hit the brakes but this ain't Nascar, it takes a long time to stop and cocks you off your "line" too when you go emergency full astern. But it gave boats just enough time to grab their very fortunate swimmers and skedaddle, though they hung on the sidelines just long enough to see the bow-to-bow collision between the tows before bugging out. That collision aspect was fortunate since the bow rakes are the only part of those barges where there ain't oil. So no spill, but a real fender-bender. now, that would have made the commercial vessel stats but not the recreational stats. So nothing in accident stats tells you the "whole story" but this one really could have made the news and in a bad way (deaths, big oil spill) if things had gone wrong.
Anyway, hope the stats are interesting, and might provoke a discussion?