At close range you can not leave the helm and even more so hull. The spire is losing armor in 4.5 seconds of firing Gatling and falling apart with volley of flak cannon. If an engineer sitting on hull, it will give you an even 2.2 seconds.
At long range it better, but you still can be destroyed long-range guns, as the Spire profile that is easy to get into.
In addition, leaving the helm you can not adjust the direction, and thus lose the ability to shoot.
In short, it is only good for games against inexperienced pilots.