I usually ride with my dad, brother, and good friend who may as well be my brother... Ocasionally we have another friend join, and as was said, chemistry is there, we have a great time, limited stops, and I feel comfortable knowing if something went wrong, I am with the right group of people.
Depending on conditions and riders, we have had some great rides with 7-8 people.
I also ride a lot with just 2 of us, and we cover a lot of area, and are usually right on eachothers bumpers... But a few years past my buddy and I had an epic day, broke trail to the top, dropped in the next canyon and my sled let go... No trail out the bottom, late in the afternoon... We made what we thought was the right decision at the time, I broke trail out on my buddies sled, and came back and towed mine out... Things worked out, but the situation was not good and could have turned ugly in a hurry... In hindsite, we didn't have many other options as I don't think we could have broken trail riding double, but I still have that day etched in my mind, and I am much more conscious of situations, especially with just 2 people.
Just a few weeks ago we invited 2 guys whom we ride dirtbikes with "good riders" only to have them bring a whole group, and a girl... Snow was bottomless... We sent 3 back because of sled issues, and had a good ride... But they were beer drinkers and we could not even take our goggles off without them cracking open a beer... All were good riders, and we all helped eachother out... But I couldn't help but think of how prepared they would be if something happened.
Some of them think we are Azzholes for not inviting them anymore, but I don't want to ride with people like that.