My Drain Pipe outside the house has been damaged severely by tree roots.
Will it be better to replace it wit PVC or Cast Iron?

What are the advantages and Disadvantages of using Cast Iron?

My Drain Pipe outside the house has been damaged severely by tree roots.
Will it be better to replace it wit PVC or Cast Iron?

What are the advantages and Disadvantages of using Cast Iron?
For below ground usage cast iron has no known advantages.

It is used mostly today for commercial jobs where fire-stopping is a concern -- Or in residential applications where sound-proofing on vertical runs is a concern.

Stick with PVC or ABS for below ground applications -- It's far cheaper and less prone to joint separation below ground than cast iron.

Growler gave you top notch advice about cast iron sewer pipes. Go with plastic. For short term relief from your root problem try this.
For immediate relief and to kill the existing roots and prevent further growth you can purchase RootX or Robics Foaming Root Killer that contain Dichlobrnic.
A less expensive way would be to call around to garden supply stores and ask for fine grain Copper Sulphate. Put a 1/2 pound in your toilet and flush it down. Repeat in 6 months id necessary. Good luck, Tom