A medium of communication can influence a lot upon the decision-making process. For instance, when using the air as a medium (face to face meetings), only one person can talk at a time simultaneously, otherwise, the members will have trouble hearing each other. The limitation may slow down decision-making process when groups using face to face trying to negotiate.
On the other hand, face to faca meetings can pass very effectively non-verbal communication, and therefore help the communication be more precise.