What next?

Yeah, I am not surprised, and especially as there are different schools of thoughts regarding, "what's best." 

At some point when I was told, "the decision is yours," I asked my oncologist this: "If you, with all of your training an knowledge are unable to make a clear recommendation either way, how am I expected to?" This led to a conversation where he explained that statistically, my chances were the same either way, which was why he was leaving it entirely in my hands. We then spoke of side effects and things that are irrelevent to the decision you are facing.

If the reason you have been left to decide for yourself is the same, then it's time to look to the personal rather than the general. For some women, knowing they have gone the whole way and done everything they can to block that breast from ever giving trouble by having a mastectomy is the highest priority over everything a mastectomy entails. For others, conserving the breast is the highest priority and since it would seem that radiotherapy can offer them the same long term outcome as a mastectomy, they would opt for that, willing to take on radiotherapy's side effects and possibly long effects.

If I were you, I would research radiotherapy thoroughly so you know what this might entail. Similarly I would look into mastectomies, both short term and long term body effects. Side by side I would list the pros and cons for each option.

At some point in all of this a direction might emerge that would tell you where you want to go.

Hi, in addition to GreyCats advice, I'd suggest you make sure you have had enough time with your consultant to talk through all your questions and really understand their perspective.  Sometimes these things can feel rushed or you think of things afterwards so it's important to follow up and decide once you know you've had the chance to discuss all the pros and cons. Good luck, it's a tough position to be in