Depends on what you hope to accomplish with batteries/solar. These units combine a battery, inverter, charger, and solar charge controller and often work well when used within their limits- many skoolie builds I've seen use such systems with much success. However, if your use case exceeds the limits of those systems you will be disappointed.
Building your own requires patience, research and a willingness to learn but will result in a more capable, more cost effective system. On the other hand, some people need very little, and just want something simple to manage.