If you’re a beginner or even an intermediate bodybuilder, you don’t need to do bent-over laterals. If you include some form of row, your posterior, or rear, deltoid—the muscle that the bent-over lateral primarily targets—will get plenty of work. When you’re concentrating on building bigger muscles throughout your physique, keep your primary focus on the big exercises.
Why not do lots of isolation exercises and plenty of the big, basic moves to get the best of both worlds? Because it would make your workouts too long and spread your limited effort and recuperation abilities over too much exercise.
If you are at an advanced level of development and your rear delts are lagging behind the surrounding musculature, use the bent-over lateral raise. Work it with both arms together, which is the common way of performing it, but keep your technique strict so you fully engages your posterior deltoids. The way that many bodybuilders do this exercise—with loose technique and a lot of momentum—their rear delts don’t get much work, so the risk of injury is greatly increased.