Internal vs External Restrained Ductile Iron Pipes joints.

I would like ​to know the ​advantages and ​disadvantages ​of using ​internally ​restrained ​ductile iron ​pipe ​joints compared ​to the ​externally ​restrained ​ductile iron ​pipe joints in any #Pipelines  project. ​  ​

What are the ​maintenance ​disadvantages ​of both these ​approaches? ​  ​

How difficult ​is it to ​dismantle both ​types of these ​joints? ​

Please share ​your experience ​with both ​internally and ​externally ​restrained ​ductile iron ​pipes.  ​
Which do you ​think give ​better results? ​