Although weight in the life raft is helpful, it's the ballast system that keeps the life raft stabilized.
You can't go wrong with the Switlik SAR6 toroidal ballast system. We used life rafts with toroidal ballast in the USCG and they are by far the best ballast around. We air dropped these to survivors because they stayed where they landed. Very little drift rate. Switlik - SAR-6 Blue Water Search and Rescue Offshore Life Raft
I would say the Winslow Global Rescue
with the Cape Horn ballast system is second.
Yes, too many in a life raft can be troublesome. I know of four guys who stayed the night in a four person life raft and they practically killed each other.
I sell Elliot (which is good too), Viking, Winslow, and Switlik. Glad to help anyway I can.