Neither. I think they're both equally important.
You're right! This was a trick question to begin with. =)
The truth is, neither one of these two groups is more important than the other. It takes full cooperation from both T-cells and B-cells for our bodies to be able to defend themselves. If one type of lymphocyte were not present, the immune response of the body would probably fail, allowing the invaders to win unconditionally. In all the immune actions, the teamwork between B-cells and T-cells is obvious. For example, notice how the Helper T cells make it possible for the B-cells to produce antibodies. Without those T lymphocytes, the B-cells would be unable to take part in the destruction of a target. You can think of these cells as partners and best buds.
