Doing it by yourself, you need to tote lots of drink and some food along, or stop and buy stuff, in which case, you need to tote your 40-lb lock along. And on organized rides, they may have a certain amount of traffic control that can help you out. And you're probably a bit safer if you're one of 500 riders than if you're a lone rider on the road. In other words, it ought to be easier on an organized ride. It's still a century either way.