Arm balances are an excellent - and ninja - way to build strength in the arms and wrists, but also to improve your proprioception and fine motor skills.
To allow us humans to walk upright and support much of our weight on our two legs, the hip joints are designed to be robust and stable. The shoulder on the other hand is extremely mobile, and therefore requires support from the surrounding soft tissues – muscles, tendons and ligaments.
Because the joint is so unstable, shoulders are prone to pain and injury. This needs to be considered when practising any arm balance, as it’s easy to just collapse into the pose, without considering the necessity of having to lift up through the midline. Abdominal strength is required in order to stabilise the torso and allow the pelvis and legs to come off the ground to achieve this type of posture. In other words, you’re equally going to have to work those abs in order to take flight.
Muscles are strengthened in the range of motion in which you work them, so it's good to mix things up and move in different ways to create new movement patterns. Don't get hung up on the end result - focus on the progressions (kramas) along the way and take them as stepping stones paving the way towards where you want to get to. In other words, they're huge achievements in their own right. Never skip the basics!!!