If you had cancer in your other breast I can't imagine why they would suggest a lumpectomy on one and mastectomy on the other. You will need to wear a prosthesis for balance andcto avoid back issues..if the other breast has a small tumor and no nodes you may be able to avoid radiotherapy with a mastectomy. Ask your surgeon about this.
The recovery is a bit longer but not by much.
I had a bilateral with reconstruction.
It does reduce the risk of a new primary cancer in a different spot of the breast. It doesnt show much difference in stats in regards to preventing metastases.
One bonus is no more mammograms needed ever again.