Buy both a 1/4"-square drive and a 1/2"- square drive torque wrench, the small one for low torque fasteners (handle bars, stems, etc) and the larger one for high torque requirements (bottom brackets, crank arms). Beam type wrenches are much less expensive and are very durable.

BTW, this question comes up here often. A search should lead to numerous threads on the pros and cons of various types and the need for them at all. I'm in the "use one" camp.