One of the things that most differentiates improvisational comedy from stand-up is that the former is done with a group of people, while the latter is usually a solo act. Sure, there are other contrasting characteristics such as the format and pace, but the number of people on stage makes a difference.
The positive attributes are pretty apparent. For one, there is safety in numbers. Where you might get stuck in a scene, your cast mate is there to help pick you up. Also, there is a less pressure to always be "on". Someone may have a better connection with the audience one night than you. That changes your job to simply feeding them great situations or lines. Probably one of the most benficial aspects of group comedy - from a performance stand point - is the idea of play. Essentially, you are just playing make-believe with each other on stage. The more fun you have with each other, than the more fun your scene is to watch. The audience can feel that synergy.
Of course, there are some negtives to performing with a group of people. For one thing, you have multiple personalities and opinions. Everyone wants a say, but often times few want to listen. This can be a problem. It's rarely ONE big thing that breaks up a group. It's a series of little things that happen that start to accumulate. Seemingly insignificant things like rehearsal times, tardiness, a tone of voice while giving suggestions, number of one person's lines in a scene versus others, etc., etc., etc.. Sometimes being in a group can be exhausting, especially if it's tempermental.
What I've found, however, is this: it is better to have a group that cares enough to disagree than to have one that simply acquiesces and inevitably falls prey t0 the mediocrity of indifference. Sure, you have to be alert as to what you're saying and how you're saying it. Sure, you have to deal with a variety of tempers - aggressive and passive-aggressive alike - but you have to stop and realize that if there is a problem, then someone sees something to fix. And if you've been together for multiple years, and still find little things to fix, then you are all - as a group - trying to be better. That is what makes group dynamics work: the acceptance of each other on the basis of a shared goal. So battle on.