Whether you book through a group or sign up by yourself, the actual gorilla trek happens in the same way. You go to the base camp, get your briefing, get divided into groups of 8 based on fitness, etc, and each group of 8 goes off in search of a different family.
Other than that, it's a personal choice. For myself, traveling solo in Rwanda was a pleasure with decent infrastructure and friendly people - certainly not disturbing or boring.
