Lots of opinions here, but in the end it's your risk analysis and willingness to get trained and keep up to date that decides for you what to carry. I'm a trained first responder and I have used a defib, but on land. We're all getting older, and at sea the chances of rescue getting to you in a timely fashion are slim. The defib might save someone's life. I carry a Philips heartstart, it's compact and self instructs the user on setup and it won't fire unless it thinks it's needed. Also, it's designed to be user maintained - battery and pads are easy to change, and it comes with a training kit. I have a pretty complete trauma kit on board to handle typical boat accidents. I also have oxygen - I've carried it for scuba accidents. A couple of years ago, we had a severe allergic reaction on a new crew but no breathing distress and we were close enough to shore to call his doctor and we administered benadryl. Turned out to be shellfish allergy he didn't know he had. Since my son-in-law's family has peanut allergies, I now carry epipens as a treatment of last resort (my doctor gave me an Rx after I described why I wanted it - he had previously helped me assemble my kit).