This info is all on my registration with the government for my PLB, and is also on the info I send to my primary and secondary contacts before a trip. I give them a specific time and date to call, allowing a day extra in case I want to stay out longer, or can self-rescue but at a slower pace. I also list alternate bail-out points in case I have to get out earlier.
For me, hiking with a group is more hazardous. That's because I am slow (and getting slower with age), and attempting to keep up with a faster group inevitably leads to falls. When alone, I hike at my own pace, take plenty of time over rough spots, and don't attempt anything beyond my current ability just because a group wants to do it--a situation I have frequently encountered on group trips.
I've also read a number of accounts in which groups got into big trouble despite supposedly experienced leaders. One prime example some years ago was a meet-up group advertised as an introduction to winter camping. The leader ignored the weather forecast (TV reporters were touting the coming weekend weather as the "winter storm of the century," which meant that it at least was not a mild storm). No effort was made to ensure that the participants had the proper gear--in fact, participants were told not to bring snowshoes, and they were not told how to keep their gear dry. They also camped in an unprotected location with poor drainage. Nobody died, but some toes were lost due to frostbite and the entire group (including leader) had to be rescued because the snow was too deep for them to walk out.
I would say that hiking alone is (assuming the leaders are far more competent than in the above example) more hazardous for inexperienced hikers. Those of us with many years' experience in varied environments (75 in my case) are probably better off solo.
I personally think the drive home after the trip is the most hazardous--the driver is tired, it's getting dark, and the road is filled with equally tired (and often inebriated) drivers trying to get home as fast as they can!
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey