This us such a biggie.....Have you had an MRI? This test can detect high DCIS and could give you the best idea of whats in the other breast.
Recovery wise it would be much the same I think having both removed or just one.
If you remove just the one, will you be able to move on and put cancer behind you, or will you worry about cancer returning in the remaining breast?
If you're considering reconstruction, some procedures can only be performed once, eg tram/diep flap can be done just once so if you do this for just one and then need to later remove and reconstruct the other, you will need to have an implant. So your new breasts will feel different to each other. But if you go for implants this wouldn't be an issue.
Good luck with your decision, you must find whats right for you and a future that's not filled with regret and worry. I'm sure lots of women will respond to help you with a variety of stories and opinions.
For what it's worth, having a mastectomy was not a bad as I imagined. Amazing what we can deal with.
Much love and hugs xxxx Louie