I find that you can get a very consistent and repeatable swath with standard lawn application guns if you practice your technique enough. Using a boom (multi-nozzle or single nozzle) doesn't totally take away swath variability. Several factors influence nozzle effective swath, one of which is height. If you're using human hands and arms to hold your boom, you're going to have to practice your technique to hold it at the right height all the time, just like you will have to practice using your lawn gun.
Is the boom more accurate than the lawn gun? NO! It's just slightly more idiot proof.