I say both depending on the context of the conversation or the question that I'm answering. As someone who had the procedure for medical reasons and spent at least a year feeling that my new penis was foreign to me, it's important to recognise that it was an event out of my control that caused it. After accepting the fact and feeling comfortable in my own skin (or lack of it in that case), I can recognise it as a characteristic too.
That's kind of how I felt, like in the time after my circumcision, like I needed to infer that it was something that was done to me and was very much an event. Time changes a lot of things, it's now a long time ago for one thing and my attitude towards it and life in general has changed. Now I see it as a characteristic of who I am.
I found my lack of choice in the matter hard to deal with at the time, but a lot of people have to accept changes to their bodies that are beyond control and in the grand scheme of things I can deal with the long term effects of being circumcised, especially as I get older and other things start to change also.
I generally that I am circumcised. Circumcision is very much part of our familys identity- it is a state that we are in. We say that our boys are circumcised rather that they were circumcised. Circumcision is very important to us and something we are very proud of. It feels very special in England where circumcision is rare for non-religious reasons, especially amongst the young. Yes, my boys and I were circumcised, but we most definitely are circumcised! Peter