@Paul Lynch Thank for reaching out to us on Microsoft Q&A.
The DR setup with ER would involve setting up two ER circuits and connecting them both to each hub network. The vnet peering is optional and helps them talk to each other but there is no disadvantage to having it except for the costs as you mentioned.
Hope this answers your question. Please let us know if you have any further questions/concerns and we will be glad to assist you. Thank you!
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