In rows, studies have shown that the further back you go, the more discipline problems there are. The visual, aural and physical stimulation from the teacher is increasingly diminished as you move further back. This allows boredom to set in, and as a result, potential disruption.
In groups, the opposite is true. Students are over stimulated–by the peers that are now not only next to him/her, but across the table! There is now MORE to distract the student, leaving it harder for the teacher to keep the student focused on any frontal instruction.
An alternative is to arrange the chairs/tables into a three-sided “box”shape (|_|), (with an occasional second row if room demands). In this fashion, EVERY STUDENT IS IN THE FIRST ROW! The teacher can freely move around the room while talking, and therefore giving “personal”contact with each student. The result: greater attention and fewer discipline problems. Desks/tables can be moved into cooperative learning groups as needed usually within two-three minutes!