I'd use the brown rice. I make a risotto with ordinary long grain rice - it doesn't have the creamy texture but does get a lovely flavour (I brown the rice and onions first before adding the stock etc). It has the big advantage for me that it is just as delicious cold the next day, for my lunch.
In all honesty, it's probably more of a savoury rice than a pukka risotto, but it's my mum's recipe and she called it risotto, so who am I to argue??!!