Should I select Air 1 control even if their flashes are compatible with Air 2 control?

We would generally recommend Air 1 control for explorative photographers that want to be free to make changes anywhere (on the lights or on the remote) but maybe don´t care so much about what exact power setting each light has. If Air 1 control is selected it doesn´t matter where or flash power is changed since the flash power changes are only incremental and no flash power is displayed on the remote. This means photographer is free to change power anywhere –from remote and/or on individual lights without caring.  If you mix AirX flashes which can use Air 2 you can see the absolute power for those, while  with non-AirX flashes with Air 1 then you will not be able to see the absolute power. 

Air 2 control is a better choice for photographers that want to be in full control from the camera. But with Air 2 control selected you are also almost fully restricted to control all the lights from the remote. It is still possible to go and manually change the flash power on one of the lights but this change will be overruled the next time you press any button on the remote.